Method and device for signaling information related to slice in image/video encoding/decoding system

ABSTRACT

A method by which a video decoding device decodes a video, according to the present document, can comprise the steps of: parsing, from a bitstream, number information related to the number of slices of which the height within a tile of a current picture is explicitly signaled; parsing, from the bitstream, on the basis of the number information, height information related to the height of the slices of which the height is explicitly signaled; deriving the number of slices in the tile on the basis of the number information and the height information; generating prediction samples by predicting the current block of the current picture on the basis of the slices within the tile; generating reconstructed samples on the basis of the prediction samples; and generating a reconstructed picture for the current picture on the basis of the reconstructed samples.

This application is a Continuation Application of InternationalApplication No. PCT/KR2020/016891, filed on Nov. 26, 2020, which claimsthe benefit of U.S. Provisional Application No. 62/941,845, filed onNov. 28, 2019, the contents of which are all hereby incorporated byreference herein in their entirety.

BACKGROUND OF THE DISCLOSURE Field of the Disclosure

The present disclosure relates to a method and apparatus for enhancingsignaling of information related to slices in a system encoding/decodingan image/video.

Related Art

Recently, the demand for high resolution, high quality image/video suchas 4K, 8K or more Ultra High Definition (UHD) image/video is increasingin various fields. As the image/video resolution or quality becomeshigher, relatively more amount of information or bits are transmittedthan for conventional image/video data. Therefore, if image/video dataare transmitted via a medium such as an existing wired/wirelessbroadband line or stored in a legacy storage medium, costs fortransmission and storage are readily increased.

Moreover, interests and demand are growing for virtual reality (VR) andartificial reality (AR) contents, and immersive media such as hologram;and broadcasting of images/videos exhibiting image/video characteristicsdifferent from those of an actual image/video, such as gameimages/videos, are also growing.

Therefore, a highly efficient image/video compression technique isrequired to effectively compress and transmit, store, or play highresolution, high quality images/videos showing various characteristicsas described above.

SUMMARY OF THE DISCLOSURE Technical Objects

A technical object of the present disclosure is to provide a method andapparatus for increasing coding efficiency of an image/video.

Another technical object of the present disclosure is to provide amethod and apparatus for efficiently signaling information on a slicewithin a tile.

Yet another technical object of the present disclosure is to provide amethod and apparatus for reducing signaling overhead when delivering (ortransferring) information on a slice within a tile.

Yet another technical object of the present disclosure is to provide amethod and apparatus for efficiently delivering (or transferring)information related to a number and height of slices within a tile.

Yet another technical object of the present disclosure is to provide amethod and apparatus for more efficiently signaling heights ofcorresponding slides, when two or more slides have the same heightwithin a tile.

Technical Solutions

According to an embodiment of the present disclosure, provided herein isa video decoding method performed by a video decoding apparatus. Themethod may include the steps of parsing number information related to anumber of slices each having its height explicitly signaled within atile of a current picture from a bitstream, parsing height informationrelated to heights of slices each having its height explicitly signaledfrom the bitstream based on the number information, deriving a number ofslices within the tile based on the number information and the heightinformation, generating prediction samples by performing prediction on acurrent block of the current picture based on the slices within thetile, generating reconstructed samples based on the prediction samples,and generating a reconstructed picture for the current picture based onthe reconstructed samples, wherein the height information may include asame number of syntax elements as a value of the number information,wherein, based on the number information value being equal to n, heightsof a 0-th slice to an (n−1)-th slice within the tile may be derivedbased on the syntax elements, wherein a height of an n-th slice withinthe tile may be derived based on the height of the (n−1)-th slice, andwherein a height of a last slice within the tile may be derived based ona remaining height after subtracting the heights of other slices withinthe tile from a height of the tile.

According to another embodiment of the present disclosure, providedherein is a video encoding method performed by a video encodingapparatus. The method may include the steps of deriving slices within atile of a current picture, generating prediction samples by performingprediction on a current block based on the derived slices, generatingresidual information based on the prediction samples and an originalpicture, generating number information related to a number of sliceseach having its height explicitly signaled within the tile and heightinformation related to heights of the slices each having its heightexplicitly signaled based on the derived slices, and encoding imageinformation including the residual information, the number information,and the height information, wherein, based on a value of the numberinformation being equal to n, the height information may indicateheights of a 0-th slice to an (n−1)-th slice within the tile, wherein aheight of an n-th slice within the tile may be derived based on theheight of the (n−1)-th slice, and wherein a height of a last slicewithin the tile may be derived based on a remaining height aftersubtracting the heights of other slices within the tile from a height ofthe tile.

According to yet another embodiment of the present disclosure, providedherein is a computer readable digital recording medium havinginformation stored therein that causes a video decoding method to beperformed by a video decoding apparatus. The video decoding method mayinclude the steps of parsing number information related to a number ofslices each having its height explicitly signaled within a tile of acurrent picture from image information, parsing height informationrelated to heights of slices each having its height explicitly signaledfrom the image information based on the number information, deriving anumber of slices within the tile based on the number information and theheight information, generating prediction samples by performingprediction on a current block of the current picture based on the sliceswithin the tile, generating reconstructed samples based on theprediction samples, and generating a reconstructed picture for thecurrent picture based on the reconstructed samples, wherein the heightinformation may include a same number of syntax elements as a value ofthe number information, wherein, based on the number information valuebeing equal to n, heights of a 0-th slice to an (n−1)-th slice withinthe tile may be derived based on the syntax elements, wherein a heightof an n-th slice within the tile may be derived based on the height ofthe (n−1)-th slice, and wherein a height of a last slice within the tilemay be derived based on a remaining height after subtracting the heightsof other slices within the tile from a height of the tile.

Effects of the Disclosure

According to an embodiment of the present disclosure, overallcompression efficiency of an image/video may be enhanced.

According to an embodiment of the present disclosure, information on aslice within a tile may be efficiently signaled.

According to an embodiment of the present disclosure, signaling overheadmay be reduced when delivering (or transferring) information on a slicewithin a tile.

According to an embodiment of the present disclosure, informationrelated to a number and height of slices within a tile may beefficiently signaled.

According to an embodiment of the present disclosure, when two or moreslides have the same height within a tile, signaling of heightinformation of the slides having the same height may be skipped.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an example of a video/image codingsystem to which embodiments of the present document are applicable.

FIG. 2 is a diagram schematically illustrating a configuration of avideo/image encoding apparatus to which the embodiments of the presentdocument are applicable.

FIG. 3 is a diagram schematically illustrating a configuration of avideo/image decoding apparatus to which the embodiments of the presentdocument are applicable.

FIG. 4 shows an example of a picture decoding procedure.

FIG. 5 shows an example of a picture encoding procedure.

FIG. 6 shows an example of an inter prediction based video/imageencoding method.

FIG. 7 shows a general view of an inter predictor in an encodingapparatus.

FIG. 8 shows an example of an inter prediction based video/imagedecoding method.

FIG. 9 shows a general view of an inter predictor in a decodingapparatus.

FIG. 10 and FIG. 11 respectively show general examples of a video/imageencoding method and a related component according to an embodiment ofthe present disclosure.

FIG. 12 and FIG. 13 respectively show general examples of a video/imagedecoding method and a related component according to an embodiment ofthe present disclosure.

FIG. 14 shows an example of a contents streaming system to which theembodiment of the present disclosure may be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The disclosure of the present document may be modified in various forms,and specific embodiments thereof will be described and illustrated inthe drawings. The terms used in the present document are used to merelydescribe specific embodiments, but are not intended to limit thedisclosed method in the present document. An expression of a singularnumber includes an expression of ‘at least one’, so long as it isclearly read differently. The terms such as “include” and “have” areintended to indicate that features, numbers, steps, operations,elements, components, or combinations thereof used in the document existand it should be thus understood that the possibility of existence oraddition of one or more different features, numbers, steps, operations,elements, components, or combinations thereof is not excluded.

In addition, each configuration of the drawings described in the presentdocument is an independent illustration for explaining functions asfeatures that are different from each other, and does not mean that eachconfiguration is implemented by mutually different hardware or differentsoftware. For example, two or more of the configurations may be combinedto form one configuration, and one configuration may also be dividedinto multiple configurations. Without departing from the gist of thedisclosed method of the present document, embodiments in whichconfigurations are combined and/or separated are included in the scopeof the disclosure of the present document.

The present document relates to video/image coding. For example, amethod/embodiment disclosed in the present document may be applied to amethod disclosed in a versatile video coding (VVC) standard. Inaddition, the method/embodiment disclosed in the present document may beapplied to a method disclosed in an essential video coding (EVC)standard, AOMedia Video 1 (AV1) standard, 2nd generation of audio videocoding standard (AVS2), or a next-generation video/image coding standard(e.g., H.267, H.268, etc.).

In the present document, a video may refer to a series of images overtime. A picture generally refers to the unit representing one image at aparticular time frame, and a slice/tile refers to the unit constitutinga part of the picture in terms of coding. A slice/tile may include oneor more coding tree units (CTUs). One picture may consist of one or moreslices/tiles. One picture may consist of one or more tile groups. Onetile group may include one or more tiles. A brick may represent arectangular region of CTU rows within a tile in a picture). A tile maybe partitioned into multiple bricks, each of which consisting of one ormore CTU rows within the tile. A tile that is not partitioned intomultiple bricks may be also referred to as a brick. A brick scan is aspecific sequential ordering of CTUs partitioning a picture in which theCTUs are ordered consecutively in CTU raster scan in a brick, brickswithin a tile are ordered consecutively in a raster scan of the bricksof the tile, and tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A tile is a rectangular regionof CTUs within a particular tile column and a particular tile row in apicture. The tile column is a rectangular region of CTUs having a heightequal to the height of the picture and a width specified by syntaxelements in the picture parameter set. The tile row is a rectangularregion of CTUs having a height specified by syntax elements in thepicture parameter set and a width equal to the width of the picture). Atile scan is a specific sequential ordering of CTUs partitioning apicture in which the CTUs are ordered consecutively in CTU raster scanin a tile whereas tiles in a picture are ordered consecutively in araster scan of the tiles of the picture. A slice includes an integernumber of bricks of a picture that may be exclusively contained in asingle NAL unit. A slice may consist of either a number of completetiles or only a consecutive sequence of complete bricks of one tile. Inthe present document, tile group and slice may be used interchangeably.For example, in the present document, a tile group/tile group header maybe referred to as a slice/slice header.

A pixel or a pel may mean a smallest unit constituting one picture (orimage). Also, ‘sample’ may be used as a term corresponding to a pixel. Asample may generally represent a pixel or a value of a pixel, and mayrepresent only a pixel/pixel value of a luma component or only apixel/pixel value of a chroma component.

A unit may represent a basic unit of image processing. The unit mayinclude at least one of a specific region of the picture and informationrelated to the region. One unit may include one luma block and twochroma (ex. Cb, cr) blocks. The unit may be used interchangeably withterms such as block or area in some cases. In a general case, an M×Nblock may include samples (or sample arrays) or a set (or array) oftransform coefficients of M columns and N rows. Alternatively, thesample may mean a pixel value in the spatial domain, and when such apixel value is transformed to the frequency domain, it may mean atransform coefficient in the frequency domain.

The unit may be interchangeably used with the term such as a block or anarea in some cases. Generally, an M×N block may represent samplescomposed of M columns and N rows or a group of transform coefficients.The sample may generally represent a pixel or a value of the pixel, andmay also represent only the pixel/pixel value of a luma component, andalso represent only the pixel/pixel value of a chroma component. Thesample may be used as the term corresponding to a pixel or a pelconfiguring one picture (or image).

Various embodiments related to video/image coding are presented in thepresent document, and the embodiments may be combined with each otherunless otherwise stated.

In the present document, technical features individually explained inone drawing may be individually implemented or simultaneouslyimplemented.

Hereinafter, embodiments of the present document will be described indetail with reference to the accompanying drawings. In addition, likereference numerals are used to indicate like elements throughout thedrawings, and the same descriptions on the like elements may be omitted.

FIG. 1 illustrates an example of a video/image coding system to whichthe embodiments of the present document may be applied.

Referring to FIG. 1, a video/image coding system may include a firstdevice (a source device) and a second device (a reception device). Thesource device may transmit encoded video/image information or data tothe reception device through a digital storage medium or network in theform of a file or streaming.

The source device may include a video source, an encoding apparatus, anda transmitter. The receiving device may include a receiver, a decodingapparatus, and a renderer. The encoding apparatus may be called avideo/image encoding apparatus, and the decoding apparatus may be calleda video/image decoding apparatus. The transmitter may be included in theencoding apparatus. The receiver may be included in the decodingapparatus. The renderer may include a display, and the display may beconfigured as a separate device or an external component.

The video source may acquire video/image through a process of capturing,synthesizing, or generating the video/image. The video source mayinclude a video/image capture device and/or a video/image generatingdevice. The video/image capture device may include, for example, one ormore cameras, video/image archives including previously capturedvideo/images, and the like. The video/image generating device mayinclude, for example, computers, tablets and smartphones, and may(electronically) generate video/images. For example, a virtualvideo/image may be generated through a computer or the like. In thiscase, the video/image capturing process may be replaced by a process ofgenerating related data.

The encoding apparatus may encode input video/image. The encodingapparatus may perform a series of procedures such as prediction,transform, and quantization for compaction and coding efficiency. Theencoded data (encoded video/image information) may be output in the formof a bitstream.

The transmitter may transmit the encoded image/image information or dataoutput in the form of a bitstream to the receiver of the receivingdevice through a digital storage medium or a network in the form of afile or streaming. The digital storage medium may include variousstorage mediums such as USB, SD, CD, DVD, Blu-ray, HDD, SSD, and thelike. The transmitter may include an element for generating a media filethrough a predetermined file format and may include an element fortransmission through a broadcast/communication network. The receiver mayreceive/extract the bitstream and transmit the received bitstream to thedecoding apparatus.

The decoding apparatus may decode the video/image by performing a seriesof procedures such as dequantization, inverse transform, and predictioncorresponding to the operation of the encoding apparatus.

The renderer may render the decoded video/image. The renderedvideo/image may be displayed through the display.

In the present document, the term “/” and “,” should be interpreted toindicate “and/or.” For instance, the expression “A/B” may mean “A and/orB.” Further, “A, B” may mean “A and/or B.” Further, “A/B/C” may mean “atleast one of A, B, and/or C.” Also, “A/B/C” may mean “at least one of A,B, and/or C.”

Further, in the document, the term “or” should be interpreted toindicate “and/or.” For instance, the expression “A or B” may comprise 1)only A, 2) only B, and/or 3) both A and B. In other words, the term “or”in the present document should be interpreted to indicate “additionallyor alternatively.”

Further, the parentheses used in the present document may mean “forexample”. Specifically, in case that “prediction (intra prediction)” isexpressed, it may be indicated that “intra prediction” is proposed as anexample of “prediction”. In other words, the term “prediction” in thepresent document is not limited to “intra prediction”, and “intraprediction” is proposed as an example of “prediction”. Further, even incase that “prediction (i.e., intra prediction)” is expressed, it may beindicated that “intra prediction” is proposed as an example of“prediction”.

FIG. 2 is a diagram schematically illustrating the configuration of avideo/image encoding apparatus to which the embodiments of the presentdocument may be applied. Hereinafter, what is referred to as the videoencoding apparatus may include an image encoding apparatus.

Referring to FIG. 2, the encoding apparatus 200 may include and beconfigured with an image partitioner 210, a predictor 220, a residualprocessor 230, an entropy encoder 240, an adder 250, a filter 260, and amemory 270. The predictor 220 may include an inter predictor 221 and anintra predictor 222. The residual processor 230 may include atransformer 232, a quantizer 233, a dequantizer 234, and an inversetransformer 235. The residual processor 230 may further include asubtractor 231. The adder 250 may be called a reconstructor orreconstructed block generator. The image partitioner 210, the predictor220, the residual processor 230, the entropy encoder 240, the adder 250,and the filter 260, which have been described above, may be configuredby one or more hardware components (e.g., encoder chipsets orprocessors) according to an embodiment. In addition, the memory 270 mayinclude a decoded picture buffer (DPB), and may also be configured by adigital storage medium. The hardware component may further include thememory 270 as an internal/external component.

The image partitioner 210 may split an input image (or, picture, frame)input to the encoding apparatus 200 into one or more processing units.As an example, the processing unit may be called a coding unit (CU). Inthis case, the coding unit may be recursively split according to aQuad-tree binary-tree ternary-tree (QTBTTT) structure from a coding treeunit (CTU) or the largest coding unit (LCU). For example, one codingunit may be split into a plurality of coding units of a deeper depthbased on a quad-tree structure, a binary-tree structure, and/or aternary-tree structure. In this case, for example, the quad-treestructure is first applied and the binary-tree structure and/or theternary-tree structure may be later applied. Alternatively, thebinary-tree structure may also be first applied. A coding procedureaccording to the present document may be performed based on a finalcoding unit which is not split any more. In this case, based on codingefficiency according to image characteristics or the like, the maximumcoding unit may be directly used as the final coding unit, or asnecessary, the coding unit may be recursively split into coding units ofa deeper depth, such that a coding unit having an optimal size may beused as the final coding unit. Here, the coding procedure may include aprocedure such as prediction, transform, and reconstruction to bedescribed later. As another example, the processing unit may furtherinclude a prediction unit (PU) or a transform unit (TU). In this case,each of the prediction unit and the transform unit may be split orpartitioned from the aforementioned final coding unit. The predictionunit may be a unit of sample prediction, and the transform unit may be aunit for inducing a transform coefficient and/or a unit for inducing aresidual signal from the transform coefficient.

The encoding apparatus 200 may subtract the prediction signal (predictedblock, prediction sample array) output from the inter predictor 221 orthe intra predictor 222 from the input image signal (original block,original sample array) to generate a residual signal (residual block,residual sample array), and the generated residual signal is transmittedto the transformer 232. In this case, as illustrated, a unit forsubtracting the prediction signal (prediction block, prediction samplearray) from an input image signal (original block, original samplearray) in the encoder 200 may be referred to as a subtractor 231. Thepredictor 220 may perform prediction on a processing target block(hereinafter, referred to as a current block) and generate a predictedblock including prediction samples for the current block. The predictor220 may determine whether intra prediction or inter prediction isapplied in units of a current block or CU. The predictor 220 maygenerate various kinds of information on prediction, such as predictionmode information, and transmit the generated information to the entropyencoder 240, as is described below in the description of each predictionmode. The information on prediction may be encoded by the entropyencoder 240 and output in the form of a bitstream.

The intra predictor 222 may predict a current block with reference tosamples within a current picture. The referenced samples may be locatedneighboring to the current block, or may also be located away from thecurrent block according to the prediction mode. The prediction modes inthe intra prediction may include a plurality of non-directional modesand a plurality of directional modes. The non-directional mode mayinclude, for example, a DC mode or a planar mode. The directional modemay include, for example, 33 directional prediction modes or 65directional prediction modes according to the fine degree of theprediction direction. However, this is illustrative and the directionalprediction modes which are more or less than the above number may beused according to the setting. The intra predictor 222 may alsodetermine the prediction mode applied to the current block using theprediction mode applied to the neighboring block.

The inter predictor 221 may induce a predicted block of the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. At this time, in order to decreasethe amount of motion information transmitted in the inter predictionmode, the motion information may be predicted in units of a block, asub-block, or a sample based on the correlation of the motioninformation between the neighboring block and the current block. Themotion information may include a motion vector and a reference pictureindex. The motion information may further include inter predictiondirection (L0 prediction, L1 prediction, Bi prediction, or the like)information. In the case of the inter prediction, the neighboring blockmay include a spatial neighboring block existing within the currentpicture and a temporal neighboring block existing in the referencepicture. The reference picture including the reference block and thereference picture including the temporal neighboring block may also bethe same as each other, and may also be different from each other. Thetemporal neighboring block may be called the name such as a collocatedreference block, a collocated CU (colCU), or the like, and the referencepicture including the temporal neighboring block may also be called acollocated picture (colPic). For example, the inter predictor 221 mayconfigure a motion information candidate list based on the neighboringblocks, and generate information indicating what candidate is used toderive the motion vector and/or the reference picture index of thecurrent block. The inter prediction may be performed based on variousprediction modes, and for example, in the case of a skip mode and amerge mode, the inter predictor 221 may use the motion information ofthe neighboring block as the motion information of the current block. Inthe case of the skip mode, the residual signal may not be transmittedunlike the merge mode. A motion vector prediction (MVP) mode mayindicate the motion vector of the current block by using the motionvector of the neighboring block as a motion vector predictor, andsignaling a motion vector difference.

The predictor 220 may generate a prediction signal based on variousprediction methods to be described below. For example, the predictor 220may apply intra prediction or inter prediction for prediction of oneblock and may simultaneously apply intra prediction and interprediction. This may be called combined inter and intra prediction(CIIP). In addition, the predictor may be based on an intra block copy(IBC) prediction mode or based on a palette mode for prediction of ablock. The IBC prediction mode or the palette mode may be used forimage/video coding of content such as games, for example, screen contentcoding (SCC). IBC basically performs prediction within the currentpicture, but may be performed similarly to inter prediction in that areference block is derived within the current picture. That is, IBC mayuse at least one of the inter prediction techniques described in thepresent document. The palette mode may be viewed as an example of intracoding or intra prediction. When the palette mode is applied, a samplevalue in the picture may be signaled based on information on the palettetable and the palette index.

The prediction signal generated by the predictor (including the interpredictor 221 and/or the intra predictor 222) may be used to generate areconstructed signal or may be used to generate a residual signal.

The transformer 232 may generate transform coefficients by applying atransform technique to the residual signal. For example, the transformtechnique may include at least one of a discrete cosine transform (DCT),a discrete sine transform (DST), a graph-based transform (GBT), or aconditionally non-linear transform (CNT). Here, GBT refers totransformation obtained from a graph when expressing relationshipinformation between pixels in the graph. CNT refers to transformationobtained based on a prediction signal generated using all previouslyreconstructed pixels. Also, the transformation process may be applied toa block of pixels having the same size as a square or may be applied toa block of a variable size that is not a square.

The quantizer 233 quantizes the transform coefficients and transmits thesame to the entropy encoder 240, and the entropy encoder 240 encodes thequantized signal (information on the quantized transform coefficients)and outputs the encoded signal as a bitstream. Information on thequantized transform coefficients may be referred to as residualinformation. The quantizer 233 may rearrange the quantized transformcoefficients in the block form into a one-dimensional vector form basedon a coefficient scan order and may generate information on thetransform coefficients based on the quantized transform coefficients inthe one-dimensional vector form.

The entropy encoder 240 may perform various encoding methods such as,for example, exponential Golomb, context-adaptive variable length coding(CAVLC), and context-adaptive binary arithmetic coding (CABAC). Theentropy encoder 240 may encode information necessary for video/imagereconstruction (e.g., values of syntax elements, etc.) other than thequantized transform coefficients together or separately. Encodedinformation (e.g., encoded video/image information) may be transmittedor stored in units of a network abstraction layer (NAL) unit in the formof a bitstream. The video/image information may further includeinformation on various parameter sets, such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). Also, the video/image informationmay further include general constraint information. In the presentdocument, information and/or syntax elements transmitted/signaled fromthe encoding apparatus to the decoding apparatus may be included invideo/image information. The video/image information may be encodedthrough the encoding procedure described above and included in thebitstream. The bitstream may be transmitted through a network or may bestored in a digital storage medium. Here, the network may include abroadcasting network and/or a communication network, and the digitalstorage medium may include various storage media such as USB, SD, CD,DVD, Blu-ray, HDD, and SSD. A transmitting unit (not shown) and/or astoring unit (not shown) for transmitting or storing a signal outputfrom the entropy encoder 240 may be configured as internal/externalelements of the encoding apparatus 200, or the transmitting unit may beincluded in the entropy encoder 240.

The quantized transform coefficients output from the quantizer 233 maybe used to generate a prediction signal. For example, the residualsignal (residual block or residual samples) may be reconstructed byapplying dequantization and inverse transform to the quantized transformcoefficients through the dequantizer 234 and the inverse transform unit235. The adder 250 may add the reconstructed residual signal to theprediction signal output from the inter predictor 221 or the intrapredictor 222 to generate a reconstructed signal (reconstructed picture,reconstructed block, reconstructed sample array). When there is noresidual for the processing target block, such as when the skip mode isapplied, the predicted block may be used as a reconstructed block. Theadder 250 may be referred to as a restoration unit or a restorationblock generator. The generated reconstructed signal may be used forintra prediction of a next processing target block in the currentpicture, or may be used for inter prediction of the next picture afterbeing filtered as described below.

Meanwhile, luma mapping with chroma scaling (LMCS) may be applied duringa picture encoding and/or reconstruction process.

The filter 260 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter260 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture, and store the modifiedreconstructed picture in the memory 270, specifically, in a DPB of thememory 270. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like. The filter 260 may generate variouskinds of information related to the filtering, and transfer thegenerated information to the entropy encoder 240 as described later inthe description of each filtering method. The information related to thefiltering may be encoded by the entropy encoder 240 and output in theform of a bitstream.

The modified reconstructed picture transmitted to the memory 270 may beused as a reference picture in the inter predictor 221. When the interprediction is applied through the encoding apparatus, predictionmismatch between the encoding apparatus 200 and the decoding apparatusmay be avoided and encoding efficiency may be improved.

The DPB of the memory 270 may store the modified reconstructed picturefor use as the reference picture in the inter predictor 221. The memory270 may store motion information of a block from which the motioninformation in the current picture is derived (or encoded) and/or motioninformation of blocks in the picture, having already been reconstructed.The stored motion information may be transferred to the inter predictor221 to be utilized as motion information of the spatial neighboringblock or motion information of the temporal neighboring block. Thememory 270 may store reconstructed samples of reconstructed blocks inthe current picture, and may transfer the reconstructed samples to theintra predictor 222.

FIG. 3 is a diagram for schematically explaining the configuration of avideo/image decoding apparatus to which the embodiments of the presentdocument may be applied.

Referring to FIG. 3, the decoding apparatus 300 may include andconfigured with an entropy decoder 310, a residual processor 320, apredictor 330, an adder 340, a filter 350, and a memory 360. Thepredictor 330 may include an inter predictor 331 and an intra predictor332. The residual processor 320 may include a dequantizer 321 and aninverse transformer 322. The entropy decoder 310, the residual processor320, the predictor 330, the adder 340, and the filter 350, which havebeen described above, may be configured by one or more hardwarecomponents (e.g., decoder chipsets or processors) according to anembodiment. Further, the memory 360 may include a decoded picture buffer(DPB), and may be configured by a digital storage medium. The hardwarecomponent may further include the memory 360 as an internal/externalcomponent.

When the bitstream including the video/image information is input, thedecoding apparatus 300 may reconstruct the image in response to aprocess in which the video/image information is processed in theencoding apparatus illustrated in FIG. 2. For example, the decodingapparatus 300 may derive the units/blocks based on block split-relatedinformation acquired from the bitstream. The decoding apparatus 300 mayperform decoding using the processing unit applied to the encodingapparatus. Therefore, the processing unit for the decoding may be, forexample, a coding unit, and the coding unit may be split according tothe quad-tree structure, the binary-tree structure, and/or theternary-tree structure from the coding tree unit or the maximum codingunit. One or more transform units may be derived from the coding unit.In addition, the reconstructed image signal decoded and output throughthe decoding apparatus 300 may be reproduced through a reproducingapparatus.

The decoding apparatus 300 may receive a signal output from the encodingapparatus of FIG. 2 in the form of a bitstream, and the received signalmay be decoded through the entropy decoder 310. For example, the entropydecoder 310 may parse the bitstream to derive information (e.g.,video/image information) necessary for image reconstruction (or picturereconstruction). The video/image information may further includeinformation on various parameter sets such as an adaptation parameterset (APS), a picture parameter set (PPS), a sequence parameter set(SPS), or a video parameter set (VPS). In addition, the video/imageinformation may further include general constraint information. Thedecoding apparatus may further decode picture based on the informationon the parameter set and/or the general constraint information.Signaled/received information and/or syntax elements described later inthe present document may be decoded may decode the decoding procedureand obtained from the bitstream. For example, the entropy decoder 310decodes the information in the bitstream based on a coding method suchas exponential Golomb coding, context-adaptive variable length coding(CAVLC), or context-adaptive arithmetic coding (CABAC), and outputsyntax elements required for image reconstruction and quantized valuesof transform coefficients for residual. More specifically, the CABACentropy decoding method may receive a bin corresponding to each syntaxelement in the bitstream, determine a context model by using a decodingtarget syntax element information, decoding information of a decodingtarget block or information of a symbol/bin decoded in a previous stage,and perform an arithmetic decoding on the bin by predicting aprobability of occurrence of a bin according to the determined contextmodel, and generate a symbol corresponding to the value of each syntaxelement. In this case, the CABAC entropy decoding method may update thecontext model by using the information of the decoded symbol/bin for acontext model of a next symbol/bin after determining the context model.The information related to the prediction among the information decodedby the entropy decoder 310 may be provided to the predictor (interpredictor 332 and intra predictor 331), and residual values on which theentropy decoding has been performed in the entropy decoder 310, that is,the quantized transform coefficients and related parameter information,may be input to the residual processor 320.

The residual processor 320 may derive a residual signal (residual block,residual samples, or residual sample array). Also, information onfiltering among the information decoded by the entropy decoder 310 maybe provided to the filter 350. Meanwhile, a receiving unit (not shown)for receiving a signal output from the encoding apparatus may be furtherconfigured as an internal/external element of the decoding apparatus300, or the receiving unit may be a component of the entropy decoder310. Meanwhile, the decoding apparatus according to the present documentmay be called a video/image/picture decoding apparatus, and the decodingapparatus may be divided into an information decoder(video/image/picture information decoder) and a sample decoder(video/image/picture sample decoder). The information decoder mayinclude the entropy decoder 310, and the sample decoder may include atleast one of the dequantizer 321, the inverse transformer 322, the adder340, the filter 350, the memory 360, an inter predictor 332, and anintra predictor 331.

The dequantizer 321 may dequantize the quantized transform coefficientsto output the transform coefficients. The dequantizer 321 may rearrangethe quantized transform coefficients in a two-dimensional block form. Inthis case, the rearrangement may be performed based on a coefficientscan order performed by the encoding apparatus. The dequantizer 321 mayperform dequantization for the quantized transform coefficients using aquantization parameter (e.g., quantization step size information), andacquire the transform coefficients.

The inverse transformer 322 inversely transforms the transformcoefficients to acquire the residual signal (residual block, residualsample array).

In the present document, at least one of quantization/dequantizationand/or transform/inverse transform may be omitted. When thequantization/dequantization is omitted, the quantized transformcoefficient may be referred to as a transform coefficient. When thetransform/inverse transform is omitted, the transform coefficient may becalled a coefficient or a residual coefficient or may still be calledthe transform coefficient for uniformity of expression.

In the present document, the quantized transform coefficient and thetransform coefficient may be referred to as a transform coefficient anda scaled transform coefficient, respectively. In this case, the residualinformation may include information on transform coefficient(s), and theinformation on the transform coefficient(s) may be signaled throughresidual coding syntax. Transform coefficients may be derived based onthe residual information (or information on the transformcoefficient(s)), and scaled transform coefficients may be derivedthrough inverse transform (scaling) on the transform coefficients.Residual samples may be derived based on inverse transform (transform)of the scaled transform coefficients. This may be applied/expressed inother parts of the present document as well.

The predictor 330 may perform the prediction of the current block, andgenerate a predicted block including the prediction samples of thecurrent block. The predictor may determine whether the intra predictionis applied or the inter prediction is applied to the current block basedon the information on prediction output from the entropy decoder 310,and determine a specific intra/inter prediction mode.

The predictor 330 may generate a prediction signal based on variousprediction methods to be described later. For example, the predictor mayapply intra prediction or inter prediction for prediction of one block,and may simultaneously apply intra prediction and inter prediction. Thismay be called combined inter and intra prediction (CIIP). In addition,the predictor may be based on an intra block copy (IBC) prediction modeor based on a palette mode for prediction of a block. The IBC predictionmode or the palette mode may be used for image/video coding of contentsuch as games, for example, screen content coding (SCC). IBC maybasically perform prediction within the current picture, but may beperformed similarly to inter prediction in that a reference block isderived within the current picture. That is, IBC may use at least one ofthe inter prediction techniques described in the present document. Thepalette mode may be considered as an example of intra coding or intraprediction. When the palette mode is applied, information on the palettetable and the palette index may be included in the video/imageinformation and signaled.

The intra predictor 331 may predict the current block by referring tothe samples in the current picture. The referred samples may be locatedin the neighborhood of the current block, or may be located apart fromthe current block according to the prediction mode. In intra prediction,prediction modes may include a plurality of non-directional modes and aplurality of directional modes. The intra predictor 331 may determinethe prediction mode to be applied to the current block by using theprediction mode applied to the neighboring block.

The inter predictor 332 may derive a predicted block for the currentblock based on a reference block (reference sample array) specified by amotion vector on a reference picture. In this case, in order to reducethe amount of motion information being transmitted in the interprediction mode, motion information may be predicted in the unit ofblocks, subblocks, or samples based on correlation of motion informationbetween the neighboring block and the current block. The motioninformation may include a motion vector and a reference picture index.The motion information may further include information on interprediction direction (L0 prediction, L1 prediction, Bi prediction, andthe like). In case of inter prediction, the neighboring block mayinclude a spatial neighboring block existing in the current picture anda temporal neighboring block existing in the reference picture. Forexample, the inter predictor 332 may construct a motion informationcandidate list based on neighboring blocks, and derive a motion vectorof the current block and/or a reference picture index based on thereceived candidate selection information. Inter prediction may beperformed based on various prediction modes, and the information on theprediction may include information indicating a mode of inter predictionfor the current block.

The adder 340 may generate a reconstructed signal (reconstructedpicture, reconstructed block, or reconstructed sample array) by addingthe obtained residual signal to the prediction signal (predicted blockor predicted sample array) output from the predictor (including interpredictor 332 and/or intra predictor 331). If there is no residual forthe processing target block, such as a case that a skip mode is applied,the predicted block may be used as the reconstructed block.

The adder 340 may be called a reconstructor or a reconstructed blockgenerator. The generated reconstructed signal may be used for the intraprediction of a next block to be processed in the current picture, andas described later, may also be output through filtering or may also beused for the inter prediction of a next picture.

Meanwhile, a luma mapping with chroma scaling (LMCS) may also be appliedin the picture decoding process.

The filter 350 may improve subjective/objective image quality byapplying filtering to the reconstructed signal. For example, the filter350 may generate a modified reconstructed picture by applying variousfiltering methods to the reconstructed picture, and store the modifiedreconstructed picture in the memory 360, specifically, in a DPB of thememory 360. The various filtering methods may include, for example,deblocking filtering, a sample adaptive offset, an adaptive loop filter,a bilateral filter, and the like.

The (modified) reconstructed picture stored in the DPB of the memory 360may be used as a reference picture in the inter predictor 332. Thememory 360 may store the motion information of the block from which themotion information in the current picture is derived (or decoded) and/orthe motion information of the blocks in the picture having already beenreconstructed. The stored motion information may be transferred to theinter predictor 332 so as to be utilized as the motion information ofthe spatial neighboring block or the motion information of the temporalneighboring block. The memory 360 may store reconstructed samples ofreconstructed blocks in the current picture, and transfer thereconstructed samples to the intra predictor 331.

In the present document, the embodiments described in the filter 260,the inter predictor 221, and the intra predictor 222 of the encodingapparatus 200 may be applied equally or to correspond to the filter 350,the inter predictor 332, and the intra predictor 331.

Meanwhile, the video/image coding method according to the presentdocument may be performed based on the following partitioning structure.Specifically, above described procedures of prediction, residualprocessing ((inverse) transform and (de)quantization), syntax elementcoding, and filtering may be performed based on CTU and CU (and/or TUand PU) derived based on the partitioning structure. A blockpartitioning procedure may be performed by the image partitioner 210 ofthe above-described encoding apparatus, and partitioning-relatedinformation may be (encoding) processed by the entropy encoder 240, andmay be transferred to the decoding apparatus in the form of a bitstream.The entropy decoder 310 of the decoding apparatus may derive the blockpartitioning structure of the current picture based on thepartitioning-related information obtained from the bitstream, and basedon this, may perform a series of procedures (e.g., prediction, residualprocessing, block/picture reconstruction, in-loop filtering, and thelike) for image decoding. The CU size and the TU size may be equal toeach other, or a plurality of TUs may be present within a CU region.Meanwhile, the CU size may generally represent a luma component (sample)coding block (CB) size. The TU size may generally represent a lumacomponent (sample) transform block (TB) size. The chroma component(sample) CB or TB size may be derived based on the luma component(sample) CB or TB size in accordance with a component ratio according toa color format (chroma format, e.g., 4:4:4, 4:2:2, 4:2:0 and the like)of a picture/image. The TU size may be derived based on maxTbSize. Forexample, if the CU size is larger than the maxTbSize, a plurality of TUs(TBs) of the maxTbSize may be derived from the CU, and thetransform/inverse transform may be performed in the unit of TU (TB).Further, for example, in case that intra prediction is applied, theintra prediction mode/type may be derived in the unit of CU (or CB), andneighboring reference sample derivation and prediction sample generationprocedures may be performed in the unit of TU (or TB). In this case, oneor a plurality of TUs (or TBs) may be present in one CU (or CB) region,and in this case, the plurality of TUs (or TBs) may share the same intraprediction mode/type.

Further, in the video/image coding according to the present document, animage processing unit may have a hierarchical structure. One picture maybe partitioned into one or more tiles, bricks, slices, and/or tilegroups. One slice may include one or more bricks. On brick may includeone or more CTU rows within a tile. The slice may include an integernumber of bricks of a picture. One tile group may include one or moretiles. One tile may include one or more CTUs. The CTU may be partitionedinto one or more CUs. A tile represents a rectangular region of CTUswithin a particular tile column and a particular tile row in a picture.A tile group may include an integer number of tiles according to a tileraster scan in the picture. A slice header may carryinformation/parameters that can be applied to the corresponding slice(blocks in the slice). In case that the encoding/decoding apparatus hasa multi-core processor, encoding/decoding processes for the tiles,slices, bricks, and/or tile groups may be processed in parallel. In thepresent document, the slice or the tile group may be used exchangeably.That is, a tile group header may be called a slice header. Here, theslice may have one of slice types including intra (I) slice, predictive(P) slice, and bi-predictive (B) slice. In predicting blocks in I slice,inter prediction may not be used, and only intra prediction may be used.Of course, even in this case, signaling may be performed by coding theoriginal sample value without prediction. With respect to blocks in Pslice, intra prediction or inter prediction may be used, and in case ofusing the inter prediction, only uni-prediction can be used. Meanwhile,with respect to blocks in B slice, the intra prediction or interprediction may be used, and in case of using the inter prediction, up tobi-prediction can be maximally used.

The encoding apparatus may determine the tile/tile group, brick, slice,and maximum and minimum coding unit sizes in consideration of the codingefficiency or parallel processing, or according to the characteristics(e.g., resolution) of a video image, and information for them orinformation capable of inducing them may be included in the bitstream.

The decoding apparatus may obtain information representing the tile/tilegroup, brick, and slice of the current picture, and whether the CTU inthe tile has been partitioned into a plurality of coding units. Bymaking such information be obtained (transmitted) only under a specificcondition, the efficiency can be enhanced.

Meanwhile, as described above, one picture may include a plurality ofslices, and one slice may include a slice header and slice data. In thiscase, one picture header may be further added to a plurality of slices(a slice header and a slice data set) in one picture. The picture header(picture header syntax) may include information/parameters commonlyapplicable to the picture. The slice header (slice header syntax) mayinclude information/parameters that may be commonly applied to theslice. An adaptation parameter set (APS) or a picture parameter set(PPS) may include information/parameters that may be commonly applied toone or more slices or pictures. A sequence parameter set (SPS) mayinclude information/parameters that may be commonly applied to one ormore sequences. A video parameter set (VPS) may includeinformation/parameters that may be commonly applied to multiple layers.A decoding parameter set (DPS) may include information/parameters thatmay be commonly applied to the overall video. The DPS may includeinformation/parameters related to concatenation of a coded videosequence (CVS).

A high level syntax (HLS) in the present disclosure include at least oneof the APS syntax, the PPS syntax, the SPS syntax, the VPS syntax, theDPS syntax, and the slice header syntax.

Additionally, for example, information on the partitioning andconfiguration, and so on, of a tile/tile group/brick/slice may beconfigured in an encoding apparatus based on the high level syntax andmay then be delivered (or transferred) to a decoding apparatus in abitstream format.

A picture may be partitioned to one or more tile rows and one or moretile columns A tile is a sequence of CTUs covering a rectangular regionof a picture. A tile may be partitioned to one or more bricks, and eachbrick may be configured of multiple CTU rows. A tile that is notpartitioned to a plurality of bricks may also be referred to as a brick.However, a brick being a subset of a tile is not referred to as a tile.A slice may include multiple tiles or multiple bricks of a tile.

FIG. 4 shows an example of a picture decoding procedure.

In image/video coding, a picture that configures an image/video may beencoded/decoded according to a decoding order. A picture order thatcorresponds to an output order of a decoded picture may be configureddifferently from the decoding order. And, when performing interprediction based on the configured picture order, forward prediction aswell as reverse prediction may be performed.

FIG. 4 shows a general example of a picture decoding procedure to whichan embodiment(s) of the present disclosure can be applied. In FIG. 4,S400 may be performed by the entropy decoder 310 of the decodingapparatus that is described above in FIG. 3, S410 may be performed bythe predictor 330, S420 may be performed by the residual processor 320,S430 may be performed by the adder 340, and S440 may be performed by thefilter 350. S400 may include an information decoding procedure that isdescribed in the present specification, S410 may include an inter/intraprediction procedure that is described in the present specification,S420 may include a residual processing procedure that is described inthe present specification, S430 may include a block/picturereconstruction procedure that is described in the present specification,and S440 may include an in-loop filtering procedure that is described inthe present specification.

Referring to FIG. 4, as described above in FIG. 3, the picture decodingprocedure may generally include a procedure of obtaining an image/videoinformation (S400) from a bitstream (through decoding), a picturereconstruction procedure (S410 to S430), and an in-loop filteringprocedure (S440) for the reconstructed picture. The picturereconstruction procedure may be performed based on prediction samplesand residual samples that are obtained by performing the inter/intraprediction procedure (S410) and the residual processing procedure (S420,dequantization and inverse transform procedures on quantized transformcoefficients). By performing an in-loop filtering procedure on thereconstructed picture that is generated by performing the picturereconstruction procedure, a modified reconstructed picture may begenerated, and the modified reconstructed picture may be outputted as adecoded picture, which is then stored in a decoding picture buffer ormemory 360 of the decoding apparatus so as to be used as a referencepicture during an inter prediction procedure when performing decoding ofa picture in a later process. In some cases, the in-loop filteringprocedure may be skipped. And, in this case, the reconstructed picturemay be outputted as the decoded picture, which is then stored in adecoding picture buffer or memory 360 of the decoding apparatus so as tobe used as a reference picture during an inter prediction procedure whenperforming decoding of a picture in a later process. As described above,the in-loop filtering procedure (S440) may include a deblockingfiltering procedure, a sample adaptive offset (SAO) procedure, anadaptive loop filter (ALF) procedure, and/or a bi-lateral filterprocedure, and so on, and part or all of the in-loop filtering proceduremay be skipped. Additionally, one or part of the deblocking filteringprocedure, the sample adaptive offset (SAO) procedure, the adaptive loopfilter (ALF) procedure, and the bi-lateral filter procedure may besequentially applied, or all of the deblocking filtering procedure, thesample adaptive offset (SAO) procedure, the adaptive loop filter (ALF)procedure, and the bi-lateral filter procedure may be sequentiallyapplied. For example, after the deblocking filtering procedure isapplied to a reconstructed picture, the SAO procedure may be performed.Alternatively, for example, after the deblocking filtering procedure isapplied to a reconstructed picture, the ALF procedure may be performed.This may also be performed likewise in an encoding apparatus.

FIG. 5 shows an example of a picture encoding procedure.

FIG. 5 shows a general example of a picture encoding procedure to whichan embodiment(s) of the present disclosure can be applied. In FIG. 5,S500 may be performed by the predictor 220 of the encoding apparatusthat is described above in FIG. 2, S510 may be performed by the residualprocessor 230, and S520 may be performed by the entropy encoder 240.S500 may include an inter/intra prediction procedure that is describedin the present specification, S610 may include a residual processingprocedure that is described in the present specification, and S520 mayinclude an information encoding procedure that is described in thepresent specification.

Referring to FIG. 5, as described above in FIG. 2, the picture encodingprocedure may generally include a procedure of encoding information forpicture reconstruction (e.g., prediction information, residualinformation, partitioning information, and so on) and outputting theencoded information in a bitstream format, as well as a procedure ofgenerating a reconstructed picture for a current picture and a procedureof applying in-loop filtering to the reconstructed picture (optional).The encoding apparatus may derive residual samples (that are modified)from quantized transform coefficients through the dequantizer 234 andthe inverse transformer 235, and, then, the encoding apparatus maygenerate a reconstructed picture based on prediction samples, which arethe output of S500, and the (modified) residual samples. Thereconstructed picture that is generated as described above may be thesame as the above-described reconstructed picture that is generated inthe decoding apparatus. A modified reconstructed picture may begenerated by performing an in-loop filtering procedure on thereconstructed picture, which is then stored in a decoding picture bufferor memory 270 of the decoding apparatus. And, just as in the decodingapparatus, the modified reconstructed picture may be used as a referencepicture during an inter prediction procedure when encoding a picture. Asdescribed above, in some cases, part or all of the in-loop filteringprocedure may be skipped. When the in-loop filtering procedure isperformed, (in-loop) filtering related information (parameter) may beencoded in the entropy encoder 240 and then transmitted in a bitstreamformat, and the decoding apparatus may perform the in-loop filteringprocedure by using the same method as the encoding apparatus based onthe filtering related information.

By performing the above-described in-loop filtering procedure, noiseoccurring when coding an image/moving picture image, such as a blockingartifact and a ringing artifact, may be reduced, andsubjective/objective visual quality may be enhanced. Additionally, byhaving both the encoding apparatus and the decoding apparatus performthe in-loop filtering procedure, the encoding apparatus and the decodingapparatus may derive the same prediction result, increase reliability inpicture coding, and reduce the size (or amount) of data that should betransmitted for picture coding.

As described above, the picture reconstruction procedure may beperformed in the decoding apparatus as well as in the encodingapparatus. A reconstructed block may be generated for each block unitbased on intra prediction/inter prediction, and a reconstructed pictureincluding reconstructed blocks may be generated. When a currentpicture/slice/tile group is an I picture/slice/tile group, the blocksincluded in the current picture/slice/tile group may be reconstructedbased only on intra prediction. Meanwhile, when the currentpicture/slice/tile group is a P or B picture/slice/tile group, theblocks included in the current picture/slice/tile group may bereconstructed based on intra prediction or inter prediction. In thiscase, inter prediction may be applied to part of the blocks within thecurrent picture/slice/tile group, and intra prediction may be applied tothe remaining blocks. Color components of a picture may include a lumacomponent and a chroma component. And, unless it is explicitly limited(or restricted) in the present specification, the methods andembodiments that are proposed in the present specification may beapplied to the luma component and the chroma component.

Meanwhile, a(n) video/image encoding procedure that is based on interprediction may generally include, for example, the following.

FIG. 6 shows an example of an inter prediction based video/imageencoding method, and FIG. 7 shows a general view of an inter predictorin an encoding apparatus.

Referring to FIG. 6 and FIG. 7, the encoding apparatus performs interprediction on a current block (S600). The encoding apparatus may derivean inter prediction mode and motion information of the current block andgenerate prediction samples of the current block. Herein, the proceduresof determining the inter prediction mode, deriving motion information,and generating prediction samples may all be performed simultaneously,or any one of the above-mentioned procedures may be performed before theother procedure(s). For example, the inter predictor 221 of the encodingapparatus may include a prediction mode determiner 221_1, a motioninformation deriver 221_2, and a prediction sample deriver 221_3. Theprediction mode determiner 221_1 may determine a prediction mode for thecurrent block, the motion information deriver 221_2 may derive motioninformation of the current block, and the prediction sample deriver221_3 may derive prediction samples of the current block. For example,the inter predictor of the encoding apparatus may search for a blockthat is similar to the current block within a predetermined region(search region) of reference pictures through motion estimation, and,then, the inter predictor of the encoding apparatus may derive areference block having minimum difference from the current block orhaving a difference from the current block that is equal to or below apredetermined reference standard. Based on such difference, a referencepicture index indicating a reference picture in which the referenceblock is located may be derived, and a motion vector may be derivedbased on a position difference between the reference block and thecurrent block. The encoding apparatus may determine a mode that isapplied to the current block, among various prediction modes. Theencoding apparatus may compare rate-distortion (RD) costs for thevarious prediction modes and determine an optimal prediction mode forthe current block.

For example, when a skip mode or merge mode is applied to the currentblock, the encoding apparatus configures a merge candidate list, and,among the reference blocks that are indicated by the merge candidatesincluded in the merge candidate list, a reference block having minimumdifference from the current block or having a difference from thecurrent block that is equal to or below a predetermined referencestandard may be derived. In this case, a merge candidate that isassociated with the derived reference block may be selected, and mergeindex information indicating the selected merge candidate may begenerated and then signaled to the decoding apparatus. Motioninformation of the current block may be derived by using motioninformation of the selected merge candidate.

As another example, when an (A)MVP mode is applied to the current block,the encoding apparatus configures an (A)MVP candidate list, and a motionvector of a selected motion vector predictor (mvp) candidate, which isselected from mvp candidates that are included in the (A)MVP candidatelist, may be used as the mvp of the current block. In this case, forexample, the motion vector indicating a reference block that is derivedby the above-described motion estimation may be used as the motionvector of the current block, and, among the mvp candidates, an mvpcandidate having a motion vector that has the smallest difference fromthe motion vector of the current block may be the selected mvpcandidate. A motion vector difference (MVD), which is a difference thatis obtained by subtracting the mvp from the motion vector of the currentblock, may be derived. In this case, information related to the MVD maybe signaled to the decoding apparatus. Additionally, when the (A)MVPmode is applied, a value of the reference picture index may beconfigured of reference picture index information and may be separatelysignaled to the decoding apparatus.

The encoding apparatus may derive residual samples based on theprediction samples (S610). The encoding apparatus may derive theresidual samples by comparing the prediction samples with originalsamples of the current block.

The encoding apparatus encodes image information including predictioninformation and residual information (S620). The encoding apparatus mayoutput the encoded image information in a bitstream format. Theprediction information may be information related to the predictionprocedure that may include prediction mode information (e.g., skip flag,merge flag or mode index, and so on) and information related to motioninformation. The information related to the motion information mayinclude candidate selection information (e.g., merge index, mvp flag ormvp index), which is information for deriving a motion vector.Additionally, the information related to the motion information mayinclude the above-described information on the MVD and/or referencepicture index information. Additionally, the information related to themotion information may include information indicating whether L0prediction, L1 prediction, or bi-prediction is applied. The residualinformation is information related to the residual samples. The residualinformation may include information related to quantized transformcoefficients for the residual samples.

The outputted bitstream may be stored in a (digital) storage medium andthen delivered to the decoding apparatus, or the outputted bitstream maybe delivered to the decoding apparatus through a network.

Meanwhile, the above-described encoding apparatus may generate areconstructed picture (including reconstructed samples and reconstructedblock) based on the reference samples and the residual samples. This isperformed so that the encoding device can derive a prediction resultthat is the same as the prediction result obtained by the predictionprocedure performed in the decoding apparatus and, also, because thecoding efficiency may be enhanced accordingly. Therefore, the encodingapparatus may store a reconstructed picture (or reconstructed samples,reconstructed block) in a memory and may use the stored picture as areference picture for inter prediction. As described above, an in-loopfiltering procedure, and so on, may be further applied to thereconstructed picture.

A(n) video/image decoding procedure that is based on inter predictionmay generally include, for example, the following.

FIG. 8 shows an example of an inter prediction based video/imagedecoding method, and FIG. 9 shows a general view of an inter predictorin a decoding apparatus.

A decoding apparatus may perform operations that correspond to theoperations performed by the encoding apparatus. The decoding apparatusmay perform prediction on a current block based on the receivedprediction information and may derive prediction samples.

More specifically, referring to FIG. 8 and FIG. 9, the decodingapparatus may determine a prediction mode for the current block based onprediction information received from a bitstream (S800). The decodingapparatus may determine which inter prediction mode is applied to thecurrent block based on prediction mode information within the predictioninformation.

For example, whether nor not a merge mode is applied to the currentblock or whether or not an (A)MVP mode is determined may be determinedbased on a merge flag. Alternatively, one inter prediction modecandidate may be selected, from various inter prediction modecandidates, based on the merge index. The inter prediction modecandidates may include various inter prediction modes, such as a skipmode, a merge mode, and/or an (A)MVP mode, and so on.

The decoding apparatus derives motion information of the current blockbased on the determined inter prediction mode (S810). For example, whena skip mode or merge mode is applied to the current block, the decodingapparatus configures a merge candidate list, which will be describedlater on in detail, and may select one merge candidate from the mergecandidates included in the merge candidate list. The selection may beperformed based on the above-described merge index. Motion informationof the current block may be derived by using motion information of theselected merge candidate. The motion information of the selected mergecandidate may be used as the motion information of the current block.

As another example, when an (A)MVP mode is applied to the current block,the decoding apparatus configures an (A)MVP candidate list, and a motionvector of a selected motion vector predictor (mvp) candidate, which isselected from mvp candidates that are included in the (A)MVP candidatelist, may be used as the mvp of the current block. The selection may beperformed based on the above-described selection information (mvp flagor mvp index). And, in this case, an MVD of the current block may bederived based on information on the MVD, and a motion vector of thecurrent block may be derived based on the mvp of the current block andthe MVD. Additionally, a reference picture index of the current blockmay be derived based on the reference picture index information. Apicture that is indicated by the reference picture index within areference picture list related to the current block may be derived as areference picture that is being referred to for the inter prediction ofthe current block.

Meanwhile, the motion information of the current block may be derivedwithout configuring any candidate list, and, in this case, theabove-described candidate list configuration may be skipped.

The decoding apparatus may generate prediction samples for the currentblock based on the motion information of the current block (S820). Inthis case, the decoding apparatus may derive the reference picture basedon a reference picture index of the current block, and, then, thedecoding apparatus may derive prediction samples of the current block byusing samples of a reference block that is indicated by the motionvector of the current block within the reference picture. In this case,among the prediction samples of the current block, a prediction samplefiltering procedure, which will be described later on in more detail,may be further performed on all or part of the prediction samples of thecurrent block.

For example, the inter predictor 332 of the decoding apparatus mayinclude a prediction mode determiner 332_1, a motion information deriver332_2, and a prediction sample deriver 332_3. The prediction modedeterminer 332_1 may determine a prediction mode for the current blockbased on received prediction mode information, the motion informationderiver 332_2 may derive motion information (motion vector and/orreference picture index, and so on) of the current block based oninformation on the received motion information, and the predictionsample deriver 332_3 may derive prediction samples of the current block.

The decoding apparatus generates residual samples for the current blockbased on the received residual information (S830). The decodingapparatus may generate reconstructed samples for the current block basedon the prediction samples and the residual samples and generate areconstructed picture based on the generated reconstructed samples(S840). Thereafter, as described above, an in-loop filtering procedure,and so on, may be further applied to the reconstructed picture.

Meanwhile, as described above, a high level syntax (HLS) may becoded/signaled for video/image coding. A coded picture may be configuredof one or more slices. A parameter describing the coded picture issignaled within a picture header, and a parameter describing a slice issignaled within a slice header. The picture header is carried in its ownNAL unit format. And, the slice header is present at a beginning (orstarting point) of a NAL unit including a payload of the slice (i.e.,slice data).

Each picture is associated with a picture header. A picture may beconfigured of different types of slices (an intra-coded slice (i.e., Islice) and inter-coded slices (i.e., P slice and B slice)). Therefore, apicture header may include syntax elements that are needed in an intraslice of a picture and an inter slice of a picture.

A picture may be partitioned to (or divided into) sub-pictures, tiles,and/or slices. Sub-picture signaling may be present in a sequenceparameter set (SPS). And, tile and square slice signaling may be presentin a picture parameter set (PPS). Raster-scan slice signaling may bepresent in a slice header.

For example, in relation to the partitioning of a picture, syntaxelements shown below in Table 1 may be included in an SPS syntax.

TABLE 1 Descriptor seq_parameter_set_rbsp( ) {  ... subpics_present_flag u(1)  if( subpics_present_flag ) {  sps_num_subpics_minus1 u(8)   for( i = 0; i <= sps_num_subpics_minus1;i++ ) {    subpic_ctu_top_left_x[ i ] u(v)    subpic_ctu_top_left_y[ i ]u(v)    subpic_width_minus1[ i ] u(v)    subpic_height_minus1[ i ] u(v)   subpic_treated_as_pic_flag[ i ] u(1)   loop_filter_across_subpic_enabled_flag[ i ] u(1)   }  }  ... }

Syntax elements shown below in Table 2 may be included in a PPS syntax.

TABLE 2 Descriptor pic_parameter_set_rbsp( ) {  ... no_pic_partition_flag u(1)  if( !no_pic_partition_flag ) {  pps_log2_ctu_size_minus5 u(2)   num_exp_tile_columns_minus1 ue(v)  num_exp_tile_rows_minus1 ue(v)   for( i = 0; i <=num_exp_tile_columns_minus1; i++ )    tile_column_width_minus1[ i ]ue(v)   for( i = 0; i <= num_exp_tile_rows_minus1; i++ )   tile_row_height_minus1[ i ] ue(v)   rect_slice_flag u(1)   if(rect_slice_flag )    single_slice_per_subpic_flag u(1)   if(rect_slice_flag && !single_slice_per_subpic_flag) {   num_slices_in_pic_minus1 ue(v)    tile_idx_delta_present_flag u(1)   for( i = 0; i < num_slices_in_pic_minus1; i++ ) {    slice_width_in_tiles_minus1[ i ] ue(v)    slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] == 0 &&       slice_height_in_tiles_minus1[ i ] == 0 ) {     num_slices_in_tile_minus1[ i ] ue(v)      numSlicesInTileMinus1 =num_slices_in_tile_minus1[ i ]      for( j = 0; j <numSlicesInTileMinus1; j++ )       slice_height_in_ctu_minus1[ i++ ]ue(v)     }     if( tile_idx_delta_present_flag && i <num_slices_in_pic_minus1 )      tile_idx_delta[ i ] se(v)    }   }  loop_filter_across_tiles_enabled_flag u(1)  loop_filter_across_slices_enabled_flag u(1)  }  ... }

In Table 2, num_slices_in_tile_minus1[i]+1 indicates a number of sliceswithin a current tile, when an i-th slice includes a subset of CTU rowsin a single tile. A value of num_slices_in_tile_minus1[i] should bewithin a range inclusive of 0 to RowHeight[tileY]−1. Herein, tileY is anindex of a tile row including an i-th slice. Whennum_slices_in_tile_minus1[i] is not present in a PPS, the value ofnum_slices_in_tile_minus1[i] is derived as 0.

slice_height_in_ctu_minus1[i]+1 indicates a height of an i-threctangular slice in CTU row units, when an i-th slice includes a subsetof CTU rows in a single tile. A value of slice_height_in_ctu_minus1[i]should be within a range inclusive of 0 to RowHeight[tileY]−1. Herein,tileY is an index of a tile row including an i-th slice.

Syntax elements shown below in Table 3 may be included in a slice headersyntax.

TABLE 3 Descriptor slice_header( ) {  ...  if( rect_slice_flag ∥NumTilesInPic > 1 )   slice_address u(v)  if( !rect_slice_flag &&NumTilesInPic > 1 )   num_tiles_in_slice_minus1 ue(v)  ... }

Referring to Table 1 to Table 3, in the current tile and slice design, arectangular slice may include one or more tiles. Alternatively, arectangular slice may include an integer number (or whole number) of CTUrows within a single tile.

When a rectangular slice includes an integer number (or whole number) ofCTU rows within a single tile (this corresponds to a case where the tileis partitioned to two or more slices), in the current signaling, theheight of each slice is explicitly signaled. However, this type ofsignaling is not an optimal signaling method.

A layout of slices within one tile may include a case where the heightsof the slices within the tile are uniform with the exception for thelast slice and a case where the heights of the slices within the tileare not uniform. When the heights of the slices within the tile areuniform with the exception for the last slice, since the heights of allslices excluding the last slice within the tile are the same, only theheight of one slice may be simply signaled without having to explicitlysignal the height of each slice. When the heights of the slices withinthe tile are not uniform, the height of each slice within the tile needsto be signaled.

The following drawings are illustrated in order to describe the detailedexample(s) of the present specification. The detailed terms of theapparatus (or device) or the detailed terms of the signal(s)/informationspecified in the drawings are merely exemplary. And, therefore, thetechnical characteristics of the present specification will not belimited only to the detailed terms used in the following drawings.

The present specification provides the following methods in order toresolve the above-described problems. The items of each method may beindependently applied or may be applied in combination.

For example, when one tile includes two or more slices, a number ofslice heights being explicitly signaled within CTU rows may be signaled.This may be referred to as syntax element num_exp_slice_in_tile. In thiscase, syntax elements (an array of slice_row_height_minus1) for indexesstarting from 0 to num_exp_slice_in_tile−1 may be signaled. This may besignaled as ue(v) or u(v), and a number of bits signaling such syntaxelements may vary in accordance with a number of CTU rows within a tile.Herein, ue(v) represents a 0-th order Exp-Golomb-coded syntax element,and u(v) indicates that v number of bits are used, where the value of vvaries in accordance with the value of other syntax elements.

The height of each slice starting from a first slice to an n-th slicewithin the tile is given the values of slice_row_height_minus1+1starting from 0 to num_exp_slice_in_tile−1, respectively. Herein, n isequal to a number of slices being explicitly signaled within the tile(num_exp_slice_in_tile).

Although remaining CTU rows that are larger thannum_exp_slice_in_tile_minus1+1 and (explicitly) signaled last within thetile are still present, a new slice is defined within the tile. In otherwords, a slice(s) that is/are not explicitly signaled is/are presentwithin the tile. The last slice may have a height that is equal to orsmaller than the num_exp_slice_in_tile_minus1+1 that was last signaled.

As another example, when one tile includes two or more slices, a numberof slices being included in the tile may be signaled. In this case, aflag indicating whether or not the heights of each slice within the tileare uniform may be signaled. When the heights of each slice within thetile are uniform, only one slice height may be signaled from the CTUrows. The height of each slice within the tile may be derived based onthe signaled slice height. And, when the heights of each slice withinthe tile are not uniform, the heights of each slice excluding the lastslice within the tile may be explicitly signaled.

In the present specification, information on the slice(s) and/or tile(s)may include information and/or syntax element(s) disclosed in Table 1 toTable 3. Image/video information may include high level syntax (HLS)disclosed in Table 1 to Table 3, and the high level syntax (HLS) mayinclude information related to slice(s) and/or information related totile(s). The information related to slice(s) may include informationindicating one or more slices within a current picture, and theinformation related to tile(s) may include information indicating one ormore tiles within the current picture. A tile including one or moreslices and a slice including one or more tiles may be present in apicture.

As an embodiment, in order to represent a partitioned structure of apicture, syntaxes shown below in Table 4 and semantics shown below inTable 5 may be used for a PPS.

TABLE 4 Descriptor pic_parameter_set_rbsp( ) {  ... no_pic_partition_flag u(1)  if( !no_pic_partition_flag ) {  pps_log2_ctu_size_minus5 u(2)   num_exp_tile_columns_minus1 ue(v)  num_exp_tile_rows_minus1 ue(v)   for( i = 0; i <=num_exp_tile_columns_minus1; i++ )    tile_column_width_minus1[ i ]ue(v)   for( i = 0; i <= num_exp_tile_rows_minus1; i++ )   tile_row_height_minus1[ i ] ue(v)   ...   if(rect_slice_flag &&!single_slice_per_subpic_flag) {    num_slices_in_pic_minus1 ue(v)   tile_idx_delta_present_flag u(1)    for( i = 0; i <num_slices_in_pic_minus1; i++ ) {     slice_width_in_tiles_minus1[ i ]ue(v)     slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] == 0 &&       slice_height_in_tiles_minus1[ i ] == 0 ) {     num_exp_slices_in_tile[ i ] ue(v)      numExpSlicesInTile =num_exp_slices_in_tile[ i ]      for( j = 0; j < numExpSlicesInTile; j++)       exp_slice_height_in_ctu_minus1[ j ] ue(v)      i +=NumSlicesInTile[ i ]     }     if( tile_idx_delta_present_flag && i <num_slices_in_pic_minus1 )      tile_idx_delta[ i ] se(v)    }   }   ... }  ... }

TABLE 5 num_exp_slices_in_tile[ i ] plus 1 specifics the number ofexp_slice_height_in_ctu_minus1[ j ] present in the PPS. When notpresent, the value of num_exp_slices_in_tile_minus1[ i ] is inferred tobe equal to 0. exp_slice_height_in_ctu_minus1[ j ] plus 1 specifies thej-th explicitly signalled rectangular slice height in units of CTU rowsfor the case where the i-th slice contains a subset of CTU rows from asingle tile. The value of exp_slice_height_in_ctu_minus1[ j ] shall bein the range of 0 to RowHeight[ tileY ] −1, inclusive, where tileY isthe tile row index containing the slices.

Referring to Table 4 and Table 5, num_exp_slices_in_tile[i]+1 representsa number of exp_slice_height_in_ctu_minus1[j] being present in a PPS.When num_exp_slices_in_tile[i] is not present in the PPS, a value ofnum_exp_slices_in_tile_minus1[i] is derived as 0.

exp_slice_height_in_ctu_minus1[j]+1 indicates a height of a j-threctangular slice being explicitly signaled in CTU row units, when ani-th slice includes a subset of CTU rows in a single tile. A value ofexp_slice_height_in_ctu_minus1[j] should be within a range inclusive of0 to RowHeight[tileY]−1. Herein, tileY is an index of a tile rowincluding a slice.

That is, num_exp_slices_in_tile[i] may be referred to as information(number information) on a number of slices having its height explicitlysignaled within the tile of a current picture. And,exp_slice_height_in_ctu_minus1[j] may be referred to as information(height information) on a height of each slice having its heightexplicitly signaled.

The number information and the height information may be anExp-Golomb-coded syntax element.

The number information may be parsed based on information on a width andheight of a slice including the tile. When the tile includes an i-thslice, the width information of the slice including the tile maycorrespond to the syntax element slice_width_in_tiles_minus1[i], and theheight information of the slice including the tile may correspond to thesyntax element slice_height_in_tiles_minus1[i]. The i-th slice may be arectangular slice, and slices within the tile may also be partitioned torectangular slices.

For example, the encoding apparatus may generate the number informationand the height information based on the information on the slices of thecurrent picture. The number information and the height information maybe included in the image information and signaled to the decodingapparatus in a bitstream format.

When the number information is parsed from a PPS, as shown in Table 4,the decoding apparatus may parse the height information from the PPSbased on the number information. For example, when a value of the numberinformation is equal to n (wherein n is an integer equal to or largerthan 0), the decoding apparatus may parse the height information on nnumber of slices (starting from the 0-th slice to the (n−1)-th slicewithin the tile) from the PPS. The height information may indicate eachof the height of the 0-th slice to the height of the (n−1)-th slice incoding tree unit (CTU) rows.

Thereafter, the decoding apparatus may derive the heights of theremaining slices within the tile based on the height of the (n−1)-thslice. More specifically, the decoding apparatus may derive the heightsof the remaining slices excluding the last slice within the tilestarting from the n-th slice within the tile to be equal to the higherof the (n−1)-th slice. For this, the decoding apparatus may compare aremaining height of the tile, which is calculated by subtracting a sumof the heights of the slices starting from the 0-th slice to the(n−1)-th slice from a total height of the tile, so as to determinewhether the remaining height is equal to or larger than a uniform sliceheight. Herein, a uniform slice may mean slices having a uniform height(the same height) within the tile. That is, the height of a uniformslice may be the same as the height of the (n−1)-th slice.

When the remaining height of the tile is equal to or larger than theheight of a uniform slice, the height of the n-th slice may be derivedas the height of the uniform slice. And, when the remaining height ofthe tile is less than the height of a uniform slice, the height of then-th slice may be derived as the remaining height. Additionally, whenthe remaining height of the tile is equal to or larger than the heightof a uniform slice, an updated remaining height may be derived bysubtracting the height of the n-th slice from the remaining height. And,when the updated remaining height is equal to or larger than the heightof a uniform slice, the decoding apparatus may derive the height of an(n+1)-th slice as the height of a uniform slice. When the updatedremaining height is less than the height of a uniform slice, thedecoding apparatus may derive the height of the height of an (n+1)-thslice as the updated remaining height. That is, excluding the last slicewithin the tile, the height of the slices starting from the n-th sliceto the last slice may be derived as a uniform height. The height of thelast slice may be equal to or less than the height of each uniform slice(slices starting from the (n−1)-th slice to a slice immediately beforethe last slice).

As an example, when 5 slices are included in one tile, and when thenumber information indicates 3, the height information for the firstslice to the third slice within the tile may be parsed from the PPS, andthe height of the fourth slice within the tile may be derived to havethe same height as the third slice. In this case, the height of thefifth slice may be larger or less than the height of the fourth slice.

The decoding apparatus may derive a number of slices within the tile byperforming the above-described scanning procedure. When the value of thenumber information is larger than 0, the procedure of derivinginformation on the height of each slice within the tile and informationon a number of slices within the tile may be indicated as shown below inTable 5.

TABLE 6 Let tileHeight be equal to RowHeight[ tileY ]remainingHeightInCtbsY = RowHeight[ tileY ] for( j = 0; j <num_exp_slices_in_tile − 1; j++ ) {  SliceHeightInCtuMinus1[ i++ ] =exp_slice_height_in_ctu_minus1[ j ]  remainingHeightInCtbsY −=SliceHeightInCtuMinus1[ j ] } uniformSliceHeightMinus1 =exp_slice_height_in_ctu_minus1[ num_exp_slices_in_tile − 1 ] while(remainingHeightInCtbsY >= (uniformSliceHeightMinus1 + 1) ) { SliceHeightInCtuMinus1[ i++ ] = uniformSliceHeightMinus1 remainingHeightInCtbsY −= (unifomSliceHeightMinus1 + 1)  j++ }if(remainingHeightInCtbsY > 0) {  SliceHeightInCtuMinus1[ i++ ] =remainingHeightInCtbsY  j++ } NumSlicesInTile[ i ] = j

In case of a rectangular slice, a list NumCtuInSlice[i] for i of a rangeinclusive of 0 to num_slices_in_pic_minus1 may indicate a number of CTUswithin an i-th slice, matrix CtbAddrInSlice[i][j] for i of a rangeinclusive of 0 to num_slices_in_pic_minus1 and j of a range inclusive of0 to NumCtuInSlice[i]−1 indicates a picture raster-scan address of aj-th CTB within the i-th slice and may be derived as shown below inTable 7.

TABLE 7 if( subpics_present_flag && single_slice_per_subpic_flag ) { for( i = 0; i <= sps_num_subpics_minus1; i++ )   NumCtuInSlice[ i ] = 0 for( i = 0; i < PicSizeInCtbsY; i++ ) {   sliceIdx = CtbToSubPicIdx[ i]   CtbAddrInSlice[ sliceIdx ][ NumCtuInSlice[ sliceIdx ] ] = i  NumCtuInSlice[ sliceIdx ]++  } } else {  tileIdx = 0  for( i = 0; i <=num_slices_in_pic_minus1; i++ )   NumCtuInSlice[ i ] = 0  for( i = 0; i<= num_slices_in_pic_minus1; i++ ) {   tileX = tileIdx % NumTileColumns  tileY = tileIdx / NumTileColumns   if( i == num_slices_in_pic_minus1 ){    slice_width_in_tiles_minus1[ i ] = NumTileColumns − 1 − tileX   slice_height_in_tiles_minus1[ i ] = NumTileRows − 1 − tileY   num_slices_in_tile_minus1[ i ] = 0   }   if(slice_width_in_tiles_minus1[ i ] == 0 && slice_height_in_tiles_minus1[ i] == 0 ) {    ctbY = tileRowBd[ tileY ]    numSlicesInTileMinus1 =NumSlicesInTile[ i ] − 1    for( j = 0; j < numSlicesInTileMinus1; j++ ){ AddCtbsToSlice( i, tileColBd[ tileX ], tileColBd[ tileX + 1 ],   ctbY, ctbY + SliceHeightInCtuMinus1[ i ] + 1 ) ctbY +=SliceHeightInCtuMinus1[ i ] + 1 i++    }    AddCtbsToSlice( i,tileColBd[ tileX ], tileColBd[ tileX + 1 ], ctbY, tileRowBd[ tileY + 1 ])   } else    for( j = 0; j <= slice_height_in_tiles_minus1[ i ]; j++ )for( k = 0; k <= slice_width_in_tiles_minus1[ i ]; k++ ) AddCtbsToSlice( i, tileColBd[ tileX + k ], tileColBd[ tileX + k + 1 ],  tileRowBd[ tileY + j ], tileRowBd[ tileY + j + 1 ] )   if(tile_idx_delta_present_flag )    tileIdx += tile_idx_delta[ i ]   else {   tileIdx += slice_width_in_tiles_minus1[ i ] + 1    if( tileIdx %NumTileColumns == 0 ) tileIdx += slice_height_in_tiles_minus1[ i ] *NumTileColumns   }  } }

As another embodiment, in order to represent a partitioned structure ofa picture, syntaxes shown below in Table 8 and semantics shown below inTable 9 may be used for a PPS.

TABLE 8 Descriptor pic_parameter_set_rbsp( ) { ... no_pic_partition_flag u(1)  if( !no_pic_partition_flag ) {   ...   if(rect_slice_flag && !single_slice_per_subpic_flag ) {   num_slices_in_pic_minus1 ue(v)    tile_idx_delta_present_flag u(1)   for( i = 0; i < num_slices_in_pic_minus1; i++ ) {    slice_width_in_tiles_minus1[ i ] ue(v)    slice_height_in_tiles_minus1[ i ] ue(v)     if(slice_width_in_tiles_minus1[ i ] == 0 &&       slice_height_in_tiles_minus1[ i ] == 0 ) {     uniform_slice_spacing_flag[ i ] u(1)      if(uniform_slice_spacing_flag[ i ] )       slice_row_height_in_ctu_minus1[i ] ue(v)      else {       num_slices_in_tile_minus1[ i ] ue(v)      numSlicesInTileMinus1 = num_slices_in_tile_minus1[ i ]       for(j = 0; j < numSlicesInTileMinus1; j++ )       slice_height_in_ctu_minus1[ j++ ] ue(v)      }     }     if(tile_idx_delta_present_flag && i < num_slices_in_pic_minus1 )     tile_idx_delta[ i ] se(v)    }   }   ...  } ... }

TABLE 9 uniform_slice_spacing_flag[ i ] equal to 1 specifics that CTUrows are distributed uniformly across the tile and signalled using thesyntax elements uniform_slice_height_in_ctu_minus1[ i ].uniform_slice_spacing_flag[ i ] equal to 0 specifies that CTU rows mayor may not be distributed uniformly across the tile and signalled usingthe syntax elements num_slices_in_tile_minus1[ i ] andslice_height_in_ctu_minus1[ i ]. slice_rows_height_in_ctu_minus1[ i ]plus 1 specifies the height of the slice excluding the last slice of thetile in units of CTBs when uniform_slice_spacing_flag[ i ] is equalto 1. The value of slice_rows_height_in_ctu_minus1[ i ] shall be in therange of 0 to RowHeight[ tileY ] − 1, inclusive, where tileY is the tilerow index containing the slices. num_slices_in_tile_minus1[ i ] plus 1specifies the number of slices in the current tile for the case wherethe i- th slice contains a subset of CTU rows from a single tile anduniform_slice_spacing_flag[ i ] is equal to 0. The value ofnum_slices_in_tile_minus1[ i ] shall be in the range of 0 to RowHeight[tileY ] − 1, inclusive, where tileY is the tile row index containing thei-th slice. When not present, the value of num_slices_in_tile_minus1[ i] is inferred to be equal to 0. slice_height_in_ctu_minus1[ i ] plus 1specifies the height of the i-th rectangular slice in units of CTU rowsfor the case where the i-th slice contains a subset of CTU rows from asingle tile. The value of slice_height_in_ctu_minusi1[ i ] shall be inthe range of 0 to RowHeight[ tileY ] − 1, inclusive, where tileY is thetile row index containing the i-th slice.

Referring to Table 8 and Table 9, if a value ofuniform_slice_spacing_flag[i] is equal to 1, this indicates that the CTUrows are uniformly distributed (or dispersed) throughout the entire tileand are signaled by using syntax elementsuniform_slice_height_in_ctu_minus1 If the value ofuniform_slice_spacing_flag[i] is equal to 0, this indicates that the CTUrows may or may not be uniformly distributed (or dispersed) throughoutthe entire tile and are signaled by using syntax elementsnum_slices_in_tile_minus1[i] and slice_height_in_ctu_minus1[i].

When the value of uniform_slice_spacing_flag is equal to 1,slice_rows_height_in_ctu_minus1[i]+1 indicates the height of the slicesexcluding the last slice of the tile in CTB units. A value ofslice_height_in_ctu_minus1 should be within a range inclusive of 0 toRowHeight[tileY]−1. Herein, tileY is an index of a tile row includingthe slices.

num_slices_in_tile_minus1[i]+1 indicates a number of slices within thecurrent tile, when an i-th slice includes a subset of CTU rows in asingle tile, and when the value of uniform_slice_spacing_flag[i] isequal to 0. A value of num_slices_in_tile_minus1 should be within arange inclusive of 0 to RowHeight[tileY]−1. Herein, tileY is an index ofa tile row including an i-th slice. When num_slices_in_tile_minus1[i] isnot present, the value of num_slices_in_tile_minus1[i] is derived as 0.

slice_height_in_ctu_minus1[i]+1 indicates a height of an i-threctangular slice in CTU row units, when an i-th slice includes a subsetof CTU rows in a single tile. A value of slice_height_in_ctu_minus1[i]should be within a range inclusive of 0 to RowHeight[tileY]−1. Herein,tileY is an index of a tile row including an i-th slice.

For example, the encoding apparatus may generate at least one ofuniform_slice_spacing_flag, slice_rows_height_in_ctu_minus1,num_slices_in_tile_minus1, and slice_height_in_ctu_minus1 based oninformation on slices of the current picture.

When uniform_slice_spacing_flag is parsed from a PPS, as shown in Table8, the decoding apparatus may parse slice_rows_height_in_ctu_minus1 ornum_slices_in_tile_minus1 from the PPS based on a value ofuniform_slice_spacing_flag. For example, if the value ofuniform_slice_spacing_flag is equal to 1, the decoding apparatus mayparse slice_rows_height_in_ctu_minus1 from the PPS and may then derivethe parsed result as the height of the remaining slices excluding thelast slice within the tile based on the value ofslice_rows_height_in_ctu_minus1. If the value ofuniform_slice_spacing_flag is equal to 0, the decoding apparatus mayparse num_slices_in_tile_minus1 and slice_height_in_ctu_minus1 from thePPS and may derive the slices within the tile based on the parsedresult.

For example, variables NumSlicesInTileMinus1[i] andSliceHeightInCtuMinus1[i+k] that are related to the number informationand height information of slices within a tile may be derived as shownbelow. Herein, k may be within a range inclusive of 0 toNumSlicesInTileMinus1[i].

TABLE 10 if(uniform_slice_spacing_flag[ i ]) {  remainingHeightInCtbsY =RowHeight[ tileY ]  uniformSliceHeightMinus1 =slice_row_height_in_ctu_minus1[ i ]  NumSlicesInTileMinus1[ i ] = 0 while( remainingHeightInCtbsY >= (uniformSliceHeightMinus1 + 1) ) {  NumSlicesInTileMinus1[ i ]++   SliceHeightInCtuMinus1[ i++ ] =uniformSliceHeightMinus1   remainingHeightInCtbsY −=(uniformSliceHeightMinus1 + 1)  }  if(remainingHeightInCtbsY > 0 ) {  NumSlicesInTileMinus1[ i ]++   SliceHeightInCtuMinus1[ i++ ] =remainingHeightInCtbsY  } } else {  remainingHeightInCtbsY = RowHeight[tileY ]  NumSlicesInTileMinus1 [ i ] = 0  for j = 0; j <numSlicesInTileMinus1; j++ ) {   NumSlicesInTileMinus1 [ i ]++  SliceHeightInCtuMinus1[ i++ ] = slice_height_in_ctu_minus1[ j ]  remainingHeightInCtbsY −= (slice_height_in_ctu_minus1[ j ] + 1)  } if(remainingHeightInCtbsY > 0 ) {   NumSlicesInTileMinus1[ i ]++  SliceHeightInCtuMinus1[ i++ ] = remainingHeightInCtbsY  } }

In case of a rectangular slice, a list NumCtuInSlice[i] for i of a rangeinclusive of 0 to num_slices_in_pic_minus1 may indicate a number of CTUswithin an i-th slice, matrix CtbAddrInSlice[i][j] for i of a rangeinclusive of 0 to num_slices_in_pic_minus1 and j of a range inclusive of0 to NumCtuInSlice[i]−1 indicates a picture raster-scan address of aj-th CTB within the i-th slice and may be derived as shown below inTable 11.

TABLE 11 if( subpics_present_flag && single_slice_per_subpic_flag ) { for( i = 0; i <= sps_num_subpics_minus1; i++ )   NumCtuInSlice[ i ] = 0 for( i = 0; i < PicSizeInCtbsY; i ++ ) {   sliceIdx = CtbsToSubPicIdx[i ]   CtbAddrInSlice[ sliceIdx ][ NumCtuInSlice[ sliceIdx ] ] = i  NumCtuInSlice[ sliceIdx ]++  } } else {  tileIdx = 0  for(i = 0; i <=num_slices_in_pic_minus1; i++ )   NumCtuInSlice[ i ] = 0  for( i = 0; i<= num_slices_in_pic_minus1; i++ ) {   tileX = tileIdx % NumTileColumns  tileY = tileIdx / NumTileColumns   if( i == num_slices_in_pic_minus1 ){    slice_width_in_tiles minus1[ i ] = NumTileColumns − 1 − tileX   slice_height_in_tiles_minus1[ i ] = NumTileRows − 1 − tileY   num_slices_in_tile_minus1[ i ] = 0   }   if(slice_width_in_tiles_minus1[ i ] == 0 && slice_height_in_tiles_minus1[ i] == 0 ) {    ctbY = tileRowBd[ tileY ]    numSlicesInTileMinus1 =NumSlicesInTileMinus1[ i ]    for( j = 0; j < numSlicesInTileMinus1; j++) { AddCtbsToSlice( i, tileColBd[ tileX ], tileColBd[ tileX + 1 ],   ctbY, ctbY + SliceHeightInCtuMinus1[ i ] + 1 ) ctbY +=SliceHeightInCfuMinus1[ i ] + 1 i++    }    AddCtbsToSlice( i,tileColBd[ tileX ], tileColBd[ tileX + 1 ], ctbY, titleRowBd[ tileY + 1] )   } else    for( j = 0; j <= slice_height_in_tiles minus1[ i ]; j++) for( k = 0; k <= slice_width_in_tiles minus1[ i ]; k++ ) AddCtbsToSlice( i, tileColBd[ tileX + k ], tileColBd[ tileX + k + 1 ],  tileRowBd[ tileY + j ], tileRowBd[ tileY + j + 1 ] )   if(tile_idx_delta_present_flag )    tileIdx += tile_idx_delta[ i ]   else {   tileIdx += slice_with_in_tiles_minus1[ i ] + 1    if( tileIdx %NumTileColumns == 0 ) tileIdx += slice_height_in_tiles_minus1[ i ] *NumTileColumns   }  } }

FIG. 10 and FIG. 11 respectively show general examples of a video/imageencoding method and a related component according to an embodiment ofthe present disclosure.

The video/image encoding method disclosed in FIG. 10 may be performed bya(n) (video/image) encoding apparatus 200 that is disclosed in FIG. 2and FIG. 11. More specifically, for example, S1000 of FIG. 10 may beperformed by the image partitioner 210 of the encoding apparatus 200,and S1010 may be performed by the predictor 220 of the encodingapparatus 200. S1020 may be performed by the residual processor 230 ofthe encoding apparatus 200. And, S1030 and S1040 may be performed by theentropy encoder 240 of the encoding apparatus 200. The video/imageencoding method disclosed in FIG. 10 may include the embodiments thatare described above in the present specification.

More specifically, referring to FIG. 10 and FIG. 11, the imagepartitioner 210 of the encoding apparatus may derive slices within atile of a current picture (S1000). For example, the image partitioner210 may partition an input image (or picture, frame) to one or more CUs.The input image may include one or more pictures. A picture may bepartitioned to one or more tiles, bricks, slices, and/or tile groups. Aslice may include one or more bricks, tiles, and/or tile groups. A brickmay include one or more CTU rows. A tile group may include one or moretiles. A tile may include one or more CTUs. The CTU may be partitionedto one or more CUs. When a specific slice within the current picture isa rectangular slice, the image partitioner 210 may partition therectangular slice to a plurality of tiles, and, among the plurality oftiles, the image partitioner 210 may partition at least one tile andthen derive a plurality of rectangular slices.

The predictor 220 of the encoding apparatus may perform prediction on acurrent block based on the slices that are derived in the imagepartitioner 210 and may then generate prediction samples (predictionblock) and prediction related information of the current block (S1010).The predictor 220 may determine whether intra prediction is beingapplied, or whether inter prediction is being applied in the currentblock or CU units. The predictor 220 may deliver diverse informationrelated to prediction (prediction related information) to the entropyencoder 240. Herein, the prediction related information may includeinformation related to an inter prediction mode and information relatedto an intra prediction mode. When the prediction mode of the currentblock is the inter prediction mode, the prediction samples may begenerated in the inter predictor 221 of the predictor 220. And, when theprediction mode of the current block is the intra prediction mode, theprediction samples may be generated in the intra predictor 222 of thepredictor 220.

The residual processor 230 of the encoding apparatus may generateresidual samples and residual information based on prediction samplesgenerated from the predictor 220 and an original picture (originalblock, original samples) (S1020). Herein, the residual information isinformation related to the residual samples, and the residualinformation may include information related to (quantized) transformcoefficients for the residual samples.

The adder (or reconstructor) of the encoding apparatus may generatereconstructed samples (reconstructed picture, reconstructed block,reconstructed sample array) by adding the residual samples that aregenerated in the residual processor 230 and the prediction samples thatare generated in the inter predictor 221 or intra predictor 222.

The entropy encoder 240 of the encoding apparatus may generateinformation related to partitioning based on a partitioning structure,which is derived in the image partitioner 210. The partitioning relatedinformation may include information (number information) on a number ofslices each having its height explicitly signaled within a tile andinformation (height information) on a height of the slices each havingits height explicitly signaled. For example, the entropy encoder 240 maygenerate number information related to a number of slices each havingits height explicitly signaled (provided) within the tile and heightinformation related to a height of the slices each having its heightexplicitly signaled (provided) based on the slices that are derived inthe image partitioner 210 (S1030). Herein, the number information mayinclude the above-described syntax element(s) num_exp_slices_in_tileand/or num_slices_in_tile_minus1. The height information may include theabove-described syntax element(s) exp_slice_height_in_ctu_minus1,slice_rows_height_in_ctu_minus1, and/or slice_height_in_ctu_minus1.

The entropy encoder 240 may encode image information includingpartitioning related information, which includes the number informationand the height information, prediction related information, which isgenerated in the predictor 220, and/or residual information, which isgenerated in the residual processor 230 (S1040). The information that isencoded in the entropy encoder 240 may be outputted in a bitstreamformat. The bitstream may be transmitted to the decoding apparatusthrough a network or storage medium.

For example, the entropy encoder 240 may include image information,which include syntax element num_exp_slices_in_tile as the numberinformation and syntax element exp_slice_height_in_ctu_minus1 as theheight information based on the above-described Table 4 and Table 5. Theheight information may indicate the height of slices each having itsheight explicitly signaled within the tile in CTU row units, and, forthis, the height information may include syntax elements for the sliceseach having its height explicitly signaled. The number of syntaxelements being included in image information may be the same as thenumber information value.

As another example, the entropy encoder 240 may encode image informationincluding syntax elements uniform_slice_spacing_flag,num_slices_in_tile_minus1, slice_rows_height_in_ctu_minus1, and/orslice_height_in_ctu_minus1 based on the above-described Table 8 andTable 9. The syntax elements num_slices_in_tile_minus1,slice_rows_height_in_ctu_minus1, and slice_height_in_ctu_minus1 may beincluded, or may not be included in the image information based on theuniform_slice_spacing_flag value.

The entropy encoder 240 may signal the number information and the heightinformation through a picture parameter set (PPS) within the imageinformation. In this case, the entropy encoder 240 may include thenumber information and/or the height information by using an Exp-Golombmethod.

FIG. 12 and FIG. 13 respectively show general examples of a video/imagedecoding method and a related component according to an embodiment ofthe present disclosure.

The video/image decoding method disclosed in FIG. 12 may be performed bya (video/image) decoding apparatus 300 that is disclosed in FIG. 3 andFIG. 13. More specifically, for example, S1200 to S1220 of FIG. 12 maybe performed by the entropy decoder 310 of the decoding apparatus. S1230of FIG. 12 may be performed by the predictor 330 of the decodingapparatus. And, S1240 and S1250 of FIG. 12 may be performed by the adder340 of the decoding apparatus. The video/image decoding method disclosedin FIG. 12 may include the embodiments that are described above in thepresent specification.

Referring to FIG. 12 and FIG. 13, the entropy decoder 310 of thedecoding apparatus may obtain partitioning related information, residualinformation, prediction related information (inter/intra predictiondifferentiation information, intra prediction mode information, interprediction mode information, and so on), in-loop filtering relatedinformation, and so on, from a bitstream. Herein, the partitioningrelated information may include information (number information) on anumber of slices each having its height explicitly signaled, amongslices within a tile of a current picture, information (heightinformation) on the height of slices each having its height explicitlysignaled, and so on.

For example, the entropy decoder 310 may parse information (numberinformation) related to a number of slices each having its heightexplicitly signaled, among slices within a tile of a current picture,from a bitstream (S1200), and may parse information (height information)related to the height of slices each having its height explicitlysignaled from the bitstream based on the number information (S1210).More specifically, the entropy decoder 310 may parse the numberinformation and the height information from a picture parameter set(PPS) of the bitstream based on the above-described Table 4. Herein, thenumber information may be parsed based on information on a width andheight of a slice including the tile. At this point, the slice includingthe tile and/or slices within the tile may be a rectangular slice(s).The number information and the height information may beExp-Golomb-coded syntax elements. The height information may includesyntax elements for each slice having its height explicitly signaled.The number of syntax elements may be the same as the number informationvalue.

For example, the entropy decoder 310 may parse syntax elementsslice_width_in_tiles_minus1 and slice_height_in_tiles_minus1 from thepicture parameter set (PPS) based on Table 4, and the entropy decoder310 may parse syntax element num_exp_slices_in_tile from the pictureparameter set (PPS) based on the values of the syntax elementsslice_width_in_tiles_minus1 and slice_height_in_tiles_minus1. And, theentropy decoder 310 may parse a number of exp_slice_height_in_ctu_minus1that is equivalent to the value of the syntax elementnum_exp_slices_in_tile from the picture parameter set (PPS).

When the value of the number information is equal to n, the entropydecoder 310 may derive heights of a 0-th slice to an (n−1)-th slicewithin the tile based on the height information. And, the entropydecoder 310 may derive a height of an n-th slice within the tile basedon the height of the (n−1)-th slice. That is, the height of the n-thslice may be derived to be the same as the height of the (n−1)-th slice.Herein, the n-th slice may not be the last slice within the tile. Inother words, the entropy decoder 310 may derive the heights of theremaining slices (slices that are not explicitly signaled) excluding thelast slice within the tile to have the same height as the (n−1)-thslice. Therefore, the heights of the slices starting from the n-th sliceto the last slice within the tile may be uniform with the exception forthe last slice within the tile. The entropy decoder 310 may derive theheight of the last slice within the tile based on a remaining heightafter subtracting the heights of other slices within the tile from theheight of the tile. When the heights of all slices within the tile arederived, the entropy decoder 310 may derive a number of slices withinthe tile (S1220). Herein, the number of slices within the tile maycorrespond to a number of slices stating from the 0-th slice to the lastslice within the tile.

The decoding apparatus 300 may decode the current picture based onslices of the current picture being derived by performing theabove-described process. More specifically, the residual processor 320of the decoding apparatus may generate residual samples based onresidual information that is obtained from the entropy decoder 310. Thepredictor 330 of the decoding apparatus may perform inter predictionand/or intra prediction on a current block that is included in theslices within the picture based on prediction related information thatis obtained from the entropy decoder 310 so as to generate predictionsamples (S1230). The adder 340 of the decoding apparatus may generatereconstructed samples based on the prediction samples that are generatedin the predictor 330 and the residual samples that are generated in theresidual processor 320 (S1240). And, the adder 340 of the decodingapparatus may generate a reconstructed picture (reconstructed block)based on the reconstructed samples (S1250).

Thereafter, an in-loop filtering procedure, such as deblockingfiltering, SAO, and/or ALF procedures, may be applied to thereconstructed picture as needed, in order to enhancesubjective/objective picture quality.

Meanwhile, as another example, the entropy decoder 310 may parse syntaxelements slice_width_in_tiles_minus1 and slice_height_in_tiles_minus1from a picture parameter set (PPS) of a bitstream based on Table 8, andthe entropy decoder 310 may parse syntax elementuniform_slice_spacing_flag from the picture parameter set (PPS) based onvalues of the syntax elements slice_width_in_tiles_minus1 andslice_height_in_tiles_minus1. In this case, the entropy decoder 310 mayparse syntax element slice_rows_height_in_ctu_minus1 or parse syntaxelement num_slices_in_tile_minus1 from the picture parameter set (PPS)based on the value of syntax element uniform_slice_spacing_flag. Thesyntax element slice_rows_height_in_ctu_minus1 may be parsed, when thevalue of the syntax element uniform_slice_spacing_flag is equal to 1,and the syntax element num_slices_in_tile_minus1 may be parsed, when thevalue of the syntax element uniform_slice_spacing_flag is equal to 0.

When the syntax element slice_rows_height_in_ctu_minus1 is parsed, theentropy decoder 310 may derive the heights of the remaining slicesexcluding the last slice within the tile as the value ofslice_rows_height_in_ctu_minus1.

When the syntax element num_slices_in_tile_minus1 is parsed, the entropydecoder 310 may parse a number of syntax elementslice_height_in_ctu_minus1 corresponding to the value of the syntaxelement num_slices_in_tile_minus1, and the values may be each be derivedas the heights of each slice within the tile, respectively.

Although methods have been described on the basis of a flowchart inwhich steps or blocks are listed in sequence in the above-describedembodiments, the steps of the present document are not limited to acertain order, and a certain step may be performed in a different stepor in a different order or concurrently with respect to that describedabove. Further, it will be understood by those ordinary skilled in theart that the steps of the flowcharts are not exclusive, and another stepmay be included therein or one or more steps in the flowchart may bedeleted without exerting an influence on the scope of the presentdocument.

The aforementioned method according to the present document may be inthe form of software, and the encoding apparatus and/or decodingapparatus according to the present document may be included in a devicefor performing image processing, for example, a TV, a computer, a smartphone, a set-top box, a display device, or the like.

When the embodiments of the present document are implemented bysoftware, the aforementioned method may be implemented by a module(process or function) which performs the aforementioned function. Themodule may be stored in a memory and executed by a processor. The memorymay be installed inside or outside the processor and may be connected tothe processor via various well-known means. The processor may includeApplication-Specific Integrated Circuit (ASIC), other chipsets, alogical circuit, and/or a data processing device. The memory may includea Read-Only Memory (ROM), a Random Access Memory (RAM), a flash memory,a memory card, a storage medium, and/or other storage device. In otherwords, the embodiments according to the present document may beimplemented and executed on a processor, a micro-processor, acontroller, or a chip. For example, functional units illustrated in therespective figures may be implemented and executed on a computer, aprocessor, a microprocessor, a controller, or a chip. In this case,information on implementation (for example, information on instructions)or algorithms may be stored in a digital storage medium.

In addition, the decoding apparatus and the encoding apparatus to whichthe embodiment(s) of the present document is applied may be included ina multimedia broadcasting transceiver, a mobile communication terminal,a home cinema video device, a digital cinema video device, asurveillance camera, a video chat device, and a real time communicationdevice such as video communication, a mobile streaming device, a storagemedium, a camcorder, a video on demand (VoD) service provider, an OverThe Top (OTT) video device, an internet streaming service provider, a 3Dvideo device, a Virtual Reality (VR) device, an Augment Reality (AR)device, an image telephone video device, a vehicle terminal (forexample, a vehicle (including an autonomous vehicle) terminal, anairplane terminal, or a ship terminal), and a medical video device; andmay be used to process an image signal or data. For example, the OTTvideo device may include a game console, a Blu-ray player, anInternet-connected TV, a home theater system, a smartphone, a tablet PC,and a Digital Video Recorder (DVR).

In addition, the processing method to which the embodiment(s) of thepresent document is applied may be produced in the form of a programexecuted by a computer and may be stored in a computer-readablerecording medium. Multimedia data having a data structure according tothe embodiment(s) of the present document may also be stored in thecomputer-readable recording medium. The computer readable recordingmedium includes all kinds of storage devices and distributed storagedevices in which computer readable data is stored. The computer-readablerecording medium may include, for example, a Blu-ray disc (BD), auniversal serial bus (USB), a ROM, a PROM, an EPROM, an EEPROM, a RAM, aCD-ROM, a magnetic tape, a floppy disk, and an optical data storagedevice. The computer-readable recording medium also includes mediaembodied in the form of a carrier wave (for example, transmission overthe Internet). In addition, a bitstream generated by the encoding methodmay be stored in the computer-readable recording medium or transmittedthrough a wired or wireless communication network.

In addition, the embodiment(s) of the present document may be embodiedas a computer program product based on a program code, and the programcode may be executed on a computer according to the embodiment(s) of thepresent document. The program code may be stored on a computer-readablecarrier.

FIG. 14 represents an example of a contents streaming system to whichthe embodiment of the present document may be applied.

Referring to FIG. 14, the content streaming system to which theembodiments of the present document is applied may generally include anencoding server, a streaming server, a web server, a media storage, auser device, and a multimedia input device.

The encoding server functions to compress to digital data the contentsinput from the multimedia input devices, such as the smart phone, thecamera, the camcorder and the like, to generate a bitstream, and totransmit it to the streaming server. As another example, in a case inwhich the multimedia input device, such as, the smart phone, the camera,the camcorder or the like, directly generates a bitstream, the encodingserver may be omitted.

The bitstream may be generated by an encoding method or a bitstreamgeneration method to which the embodiments of the present document isapplied. And the streaming server may temporarily store the bitstream ina process of transmitting or receiving the bitstream.

The streaming server transmits multimedia data to the user equipment onthe basis of a user's request through the web server, which functions asan instrument that informs a user of what service there is. When theuser requests a service which the user wants, the web server transfersthe request to the streaming server, and the streaming server transmitsmultimedia data to the user. In this regard, the contents streamingsystem may include a separate control server, and in this case, thecontrol server functions to control commands/responses betweenrespective equipment in the content streaming system.

The streaming server may receive contents from the media storage and/orthe encoding server. For example, in a case the contents are receivedfrom the encoding server, the contents may be received in real time. Inthis case, the streaming server may store the bitstream for apredetermined period of time to provide the streaming service smoothly.

For example, the user equipment may include a mobile phone, a smartphone, a laptop computer, a digital broadcasting terminal, a personaldigital assistant (PDA), a portable multimedia player (PMP), anavigation, a slate PC, a tablet PC, an ultrabook, a wearable device(e.g., a watch-type terminal (smart watch), a glass-type terminal (smartglass), a head mounted display (HMD)), a digital TV, a desktop computer,a digital signage or the like.

Each of servers in the contents streaming system may be operated as adistributed server, and in this case, data received by each server maybe processed in distributed manner.

What is claimed is:
 1. A video decoding method performed by a videodecoding apparatus, the method comprising: parsing number informationrelated to a number of explicit slices each having its height explicitlysignaled within a tile of a current picture from a bitstream; parsingheight information related to heights of explicit slices each having itsheight explicitly signaled from the bitstream based on the numberinformation; deriving a number of slices within the tile based on thenumber information and the height information; generating predictionsamples by performing prediction on a current block of the currentpicture based on one of the slices within the tile; generatingreconstructed samples based on the prediction samples; and generating areconstructed picture for the current picture based on the reconstructedsamples, wherein a number of syntax elements in the height informationis equal to the number of the explicit slices specified by the numberinformation, wherein, based on the number of explicit slices being equalto n, heights of a 0-th slice to an (n−1)-th slice within the tile arederived based on the syntax elements in the height information, whereina height of an n-th slice within the tile is derived based on the heightof the (n−1)-th slice, and wherein a height of a last slice within thetile is derived based on a remaining height after subtracting theheights of other slices within the tile from a height of the tile. 2.The video decoding method of claim 1, wherein the number of sliceswithin the tile is equal to a number of slices stating from the 0-thslice to the last slice.
 3. The video decoding method of claim 1,wherein the height of the n-th slice is derived to be the same as theheight of the (n−1)-th slice.
 4. The video decoding method of claim 1,wherein heights of slices starting from the n-th slice to a sliceimmediately before the last slice within the tile are uniform.
 5. Thevideo decoding method of claim 4, wherein the height of the last sliceis smaller or equal to the height of the (n−1)-th slice.
 6. The videodecoding method of claim 1, further comprising: comparing a remainingheight of the tile that is calculated by subtracting a sum of theheights of the slices starting from the 0-th slice to the (n−1)-th slicefrom a total height of the tile, so as to determine whether theremaining height is equal to or larger than a height of a uniform slice,wherein the height of a uniform slice is the same as the height of the(n−1)-th slice, wherein, based on the remaining height of the tile thatis calculated by subtracting a sum of the heights of the slices startingfrom the 0-th slice to the (n−1)-th slice from a total height of thetile being equal to or larger than the height of the uniform slice, then-th slice having the height of a uniform slice is derived, and wherein,based on the remaining height of the tile that is calculated bysubtracting a sum of the heights of the slices starting from the 0-thslice to the (n−1)-th slice from a total height of the tile beingsmaller than the height of the uniform slice, the n-th slice having theremaining height is derived.
 7. The video decoding method of claim 6,wherein, based on the remaining height being equal to or larger than theheight of the uniform slice, an updated remaining height is derived,wherein the updated remaining height is updated by subtracting theheight of the n-th slice from the remaining height of the tile that iscalculated by subtracting the sum of the heights of the slices startingfrom the 0-th slice to the (n−1)-th slice from the total height of thetile, wherein, based on the updated remaining height being equal to orlarger than the height of the uniform slice, an (n+1)-th slice havingthe height of the uniform slice is derived, and wherein, based on thebased on the updated remaining height being smaller than the height ofthe uniform slice, an (n+1)-th slice having the updated remaining heightis derived.
 8. The video decoding method of claim 1, wherein the numberinformation and the height information include an Exp-Golomb-codedsyntax element.
 9. The video decoding method of claim 1, wherein thenumber information includes a syntax element num_exp_slices_in_tile, andwherein the height information includes a syntax elementexp_slice_height_in_ctu_minus1.
 10. The video decoding method of claim1, wherein slices within the tile are rectangular slices.
 11. The videodecoding method of claim 1, wherein the number information is parsedbased on information related to a width and height of a slice includingthe tile.
 12. A video encoding method performed by a video encodingapparatus, the method comprising: deriving slices within a tile of acurrent picture; generating predictions samples by performing predictionon a current block based on one of the derived slices; generatingresidual information based on the prediction samples and an originalpicture; generating number information related to a number of explicitslices each having its height explicitly signaled within the tile andheight information related to heights of the explicit slices each havingits height explicitly signaled based on the derived slices; and encodingimage information including the residual information, the numberinformation, and the height information, wherein a number of syntaxelements in the height information is equal to the number of theexplicit slices specified by the number information, wherein, based onthe number of the explicit slices being equal to n, the syntax elementsin the height information indicate heights of a 0-th slice to an(n−1)-th slice within the tile, wherein a height of an n-th slice withinthe tile is represented based on the height of the (n−1)-th slice, andwherein a height of a last slice within the tile is represented based ona remaining height after subtracting the heights of other slices withinthe tile from a height of the tile.
 13. A non-transitory computerreadable digital storage medium storing a bitstream generated by a videoencoding method, wherein the video encoding method comprises: derivingslices within a tile of a current picture; generating prediction samplesby performing prediction on a current block based on one of the derivedslices; generating residual information based on the prediction samplesand an original picture; generating number information related to anumber of explicit slices each having its height explicitly signaledwithin the tile and height information related to heights of theexplicit slices each having its height explicitly signaled based on thederived slices; and encoding image information to generate thebitstream, wherein the image information includes the residualinformation, the number information, and the height information, whereina number of syntax elements in the height information is equal to thenumber of the explicit slices specified by the number information,wherein, based on the number of the explicit slices being equal to n,the syntax elements in the height information indicate heights of a 0-thslice to an (n−1)-th slice within the tile, wherein a height of an n-thslice within the tile is represented based on the height of the (n−1)-thslice, and wherein a height of a last slice within the tile isrepresented based on a remaining height after subtracting the heights ofother slices within the tile from a height of the tile.